feat(02-04): implement admin API endpoints — user CRUD, quota management, AI config

- GET /api/admin/users: list users (safe fields only, ordered by created_at)
- POST /api/admin/users: create user (password_must_change=True, quota init)
- PATCH /api/admin/users/{id}/status: deactivate/reactivate with sole-admin guard
- POST /api/admin/users/{id}/password-reset: Celery email dispatch (no token returned)
- GET /api/admin/users/{id}/quota: quota view with MB helpers
- PATCH /api/admin/users/{id}/quota: quota adjust with below-usage warning
- PATCH /api/admin/users/{id}/ai-config: assign AI provider/model per user
- _user_to_dict() whitelist helper prevents password_hash/credentials_enc leakage
- No impersonation endpoint (ADMIN-07 enforced by omission)
- get_current_admin Depends() on every handler (SEC-07)
- Updated backend/main.py to include admin_router
- Fixed test: mock send_reset_email.delay to avoid Redis in unit tests

backend/api/admin.py

@@ -0,0 +1,380 @@
+"""
+Admin API endpoints for DocuVault.
+
+All handlers require get_current_admin (SEC-07, D-08) — no handler uses
+get_current_user alone.
+
+Implements:
+  GET    /api/admin/users                    — list all users (ADMIN-01)
+  POST   /api/admin/users                    — create user (ADMIN-01)
+  PATCH  /api/admin/users/{id}/status        — deactivate/reactivate (ADMIN-02)
+  POST   /api/admin/users/{id}/password-reset — initiate reset email (ADMIN-03)
+  GET    /api/admin/users/{id}/quota          — view quota (ADMIN-04)
+  PATCH  /api/admin/users/{id}/quota          — adjust quota (ADMIN-04)
+  PATCH  /api/admin/users/{id}/ai-config      — assign AI provider/model (ADMIN-05)
+
+Security invariants:
+  - Every handler injects Depends(get_current_admin) — verified by grep count
+  - _user_to_dict() whitelist helper prevents accidental field leakage (T-02-27)
+  - No impersonation endpoint — ADMIN-07 enforced by omission (T-02-28)
+  - Admin-created users: password_must_change=True (ADMIN-01, T-02-32)
+  - Deactivation of sole admin prevented (T-02-29)
+  - Password reset sends email via Celery; does not return token (T-02-30)
+"""
+from __future__ import annotations
+
+import re
+import uuid
+from typing import Optional
+
+from fastapi import APIRouter, Depends, HTTPException, status
+from pydantic import BaseModel, EmailStr, field_validator
+from sqlalchemy import func, select
+from sqlalchemy.ext.asyncio import AsyncSession
+
+from db.models import Quota, RefreshToken, User
+from deps.auth import get_current_admin
+from deps.db import get_db
+from services.auth import hash_password, revoke_all_refresh_tokens
+
+router = APIRouter(prefix="/api/admin", tags=["admin"])
+
+# ── Constants ─────────────────────────────────────────────────────────────────
+
+_DEFAULT_QUOTA_BYTES = 104857600  # 100 MB free-tier default (D-06)
+
+_PASSWORD_DETAIL = (
+    "Password must be at least 12 characters and include uppercase, "
+    "lowercase, a number, and a special character."
+)
+
+
+# ── Safe response helper ──────────────────────────────────────────────────────
+
+def _user_to_dict(user: User) -> dict:
+    """Return a safe subset of User fields — never includes password_hash,
+    credentials_enc, totp_secret, or any document content (T-02-27, SEC-07).
+    """
+    return {
+        "id": str(user.id),
+        "handle": user.handle,
+        "email": user.email,
+        "role": user.role,
+        "is_active": user.is_active,
+        "totp_enabled": user.totp_enabled,
+        "ai_provider": user.ai_provider,
+        "ai_model": user.ai_model,
+        "password_must_change": user.password_must_change,
+        "created_at": user.created_at.isoformat() if user.created_at else None,
+    }
+
+
+# ── Password strength helper ──────────────────────────────────────────────────
+
+def _validate_password_strength(password: str) -> None:
+    """Raise ValueError with the spec message if password fails any strength rule.
+
+    Rules (AUTH-01): min 12 chars, has uppercase, has lowercase, has digit,
+    has special char (non-alphanumeric).
+    """
+    if len(password) < 12:
+        raise ValueError(_PASSWORD_DETAIL)
+    if not re.search(r"[A-Z]", password):
+        raise ValueError(_PASSWORD_DETAIL)
+    if not re.search(r"[a-z]", password):
+        raise ValueError(_PASSWORD_DETAIL)
+    if not re.search(r"[0-9]", password):
+        raise ValueError(_PASSWORD_DETAIL)
+    if not re.search(r"[^A-Za-z0-9]", password):
+        raise ValueError(_PASSWORD_DETAIL)
+
+
+# ── Request models ────────────────────────────────────────────────────────────
+
+class UserCreate(BaseModel):
+    handle: str
+    email: EmailStr
+    password: str
+    role: str = "user"
+
+    @field_validator("password")
+    @classmethod
+    def password_strength(cls, v: str) -> str:
+        try:
+            _validate_password_strength(v)
+        except ValueError as exc:
+            raise ValueError(str(exc)) from exc
+        return v
+
+
+class UserStatusUpdate(BaseModel):
+    is_active: bool
+
+
+class QuotaUpdate(BaseModel):
+    limit_bytes: int
+
+    @field_validator("limit_bytes")
+    @classmethod
+    def must_be_positive(cls, v: int) -> int:
+        if v <= 0:
+            raise ValueError("limit_bytes must be greater than 0")
+        return v
+
+
+class AiConfigUpdate(BaseModel):
+    ai_provider: Optional[str] = None
+    ai_model: Optional[str] = None
+
+
+# ── Endpoints ─────────────────────────────────────────────────────────────────
+
+
+@router.get("/users")
+async def list_users(
+    session: AsyncSession = Depends(get_db),
+    _admin: User = Depends(get_current_admin),
+) -> dict:
+    """List all users, ordered by created_at DESC.
+
+    Response shape: { items: [...safe user fields...] }
+    Never includes password_hash, credentials_enc, or document content (T-02-27).
+    """
+    result = await session.execute(
+        select(User).order_by(User.created_at.desc())
+    )
+    users = result.scalars().all()
+    return {"items": [_user_to_dict(u) for u in users]}
+
+
+@router.post("/users", status_code=status.HTTP_201_CREATED)
+async def create_user(
+    body: UserCreate,
+    session: AsyncSession = Depends(get_db),
+    _admin: User = Depends(get_current_admin),
+) -> dict:
+    """Admin creates a new user account (ADMIN-01).
+
+    - password_must_change=True forces the user to change their password on
+      first login (T-02-32, D-06).
+    - Quota row initialized at 100 MB (D-06).
+    - Returns 409 if email or handle is already taken.
+    """
+    # Check uniqueness
+    existing_email = await session.execute(
+        select(User).where(User.email == str(body.email))
+    )
+    if existing_email.scalar_one_or_none() is not None:
+        raise HTTPException(
+            status_code=status.HTTP_409_CONFLICT,
+            detail="Email already registered",
+        )
+
+    existing_handle = await session.execute(
+        select(User).where(User.handle == body.handle)
+    )
+    if existing_handle.scalar_one_or_none() is not None:
+        raise HTTPException(
+            status_code=status.HTTP_409_CONFLICT,
+            detail="Handle already taken",
+        )
+
+    new_user = User(
+        id=uuid.uuid4(),
+        handle=body.handle,
+        email=str(body.email),
+        password_hash=hash_password(body.password),
+        role=body.role,
+        is_active=True,
+        totp_enabled=False,
+        password_must_change=True,  # ADMIN-01: force password change on first login
+    )
+    session.add(new_user)
+
+    quota = Quota(
+        user_id=new_user.id,
+        limit_bytes=_DEFAULT_QUOTA_BYTES,
+        used_bytes=0,
+    )
+    session.add(quota)
+    await session.flush()
+
+    return {
+        "id": str(new_user.id),
+        "handle": new_user.handle,
+        "email": new_user.email,
+        "role": new_user.role,
+        "created_at": new_user.created_at.isoformat() if new_user.created_at else None,
+    }
+
+
+@router.patch("/users/{user_id}/status")
+async def update_user_status(
+    user_id: uuid.UUID,
+    body: UserStatusUpdate,
+    session: AsyncSession = Depends(get_db),
+    _admin: User = Depends(get_current_admin),
+) -> dict:
+    """Deactivate or reactivate a user account (ADMIN-02).
+
+    - Prevents deactivating the last active admin (T-02-29).
+    - On deactivation: all refresh tokens are revoked (family revocation).
+    """
+    user = await session.get(User, user_id)
+    if user is None:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="User not found")
+
+    # Guard: cannot deactivate the only remaining active admin (T-02-29)
+    if not body.is_active and user.role == "admin":
+        count_result = await session.execute(
+            select(func.count(User.id)).where(
+                User.role == "admin",
+                User.is_active.is_(True),
+            )
+        )
+        active_admin_count = count_result.scalar_one()
+        if active_admin_count <= 1:
+            raise HTTPException(
+                status_code=status.HTTP_400_BAD_REQUEST,
+                detail="Cannot deactivate the only admin",
+            )
+
+    user.is_active = body.is_active
+
+    if not body.is_active:
+        # Revoke all refresh tokens on deactivation
+        await revoke_all_refresh_tokens(session, user.id)
+
+    session.add(user)
+    await session.flush()
+
+    return {
+        "id": str(user.id),
+        "handle": user.handle,
+        "email": user.email,
+        "is_active": user.is_active,
+    }
+
+
+@router.post("/users/{user_id}/password-reset", status_code=status.HTTP_202_ACCEPTED)
+async def initiate_password_reset(
+    user_id: uuid.UUID,
+    session: AsyncSession = Depends(get_db),
+    _admin: User = Depends(get_current_admin),
+) -> dict:
+    """Admin initiates a password reset for a user (ADMIN-03).
+
+    Sends the reset email via Celery. Does NOT:
+      - return a reset token (T-02-30)
+      - grant admin access to the account
+      - log in as the target user (ADMIN-07 — no impersonation)
+
+    Returns 202 immediately regardless of email delivery status.
+    """
+    user = await session.get(User, user_id)
+    if user is None:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="User not found")
+
+    from services.auth import create_password_reset_token  # noqa: PLC0415
+    from config import settings as _settings  # noqa: PLC0415
+
+    reset_token = create_password_reset_token(str(user.id))
+    reset_link = f"{_settings.frontend_url}/password-reset/confirm?token={reset_token}"
+
+    # Deferred import to avoid circular imports (same pattern as document_tasks)
+    from tasks.email_tasks import send_reset_email  # noqa: PLC0415
+    send_reset_email.delay(user.email, reset_link)
+
+    return {"message": "Password reset email sent"}
+
+
+@router.get("/users/{user_id}/quota")
+async def get_user_quota(
+    user_id: uuid.UUID,
+    session: AsyncSession = Depends(get_db),
+    _admin: User = Depends(get_current_admin),
+) -> dict:
+    """Return quota details for a user (ADMIN-04).
+
+    Quota info is admin-visible operational data — no PII, no document content
+    (T-02-31 disposition: accept).
+    """
+    quota = await session.get(Quota, user_id)
+    if quota is None:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Quota not found")
+
+    return {
+        "user_id": str(quota.user_id),
+        "limit_bytes": quota.limit_bytes,
+        "used_bytes": quota.used_bytes,
+        "limit_mb": quota.limit_bytes // 1048576,
+        "used_mb": quota.used_bytes // 1048576,
+    }
+
+
+@router.patch("/users/{user_id}/quota")
+async def update_user_quota(
+    user_id: uuid.UUID,
+    body: QuotaUpdate,
+    session: AsyncSession = Depends(get_db),
+    _admin: User = Depends(get_current_admin),
+) -> dict:
+    """Adjust a user's storage quota (ADMIN-04).
+
+    If the new limit is below current usage, still applies the change but
+    returns warning=True with an explanatory message. Uploads will be blocked
+    but existing documents are preserved.
+    """
+    quota = await session.get(Quota, user_id)
+    if quota is None:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="Quota not found")
+
+    warning = body.limit_bytes < quota.used_bytes
+    warning_message = (
+        "New limit is below current usage. Uploads will be blocked but existing documents are preserved."
+        if warning
+        else None
+    )
+
+    quota.limit_bytes = body.limit_bytes
+    session.add(quota)
+    await session.flush()
+
+    response: dict = {
+        "user_id": str(quota.user_id),
+        "limit_bytes": quota.limit_bytes,
+        "used_bytes": quota.used_bytes,
+        "warning": warning,
+    }
+    if warning_message:
+        response["message"] = warning_message
+    return response
+
+
+@router.patch("/users/{user_id}/ai-config")
+async def update_ai_config(
+    user_id: uuid.UUID,
+    body: AiConfigUpdate,
+    session: AsyncSession = Depends(get_db),
+    _admin: User = Depends(get_current_admin),
+) -> dict:
+    """Assign AI provider and model for a user (ADMIN-05).
+
+    Users cannot change their own AI provider or model (PROJECT.md Key Decision).
+    Only admins have this capability.
+    """
+    user = await session.get(User, user_id)
+    if user is None:
+        raise HTTPException(status_code=status.HTTP_404_NOT_FOUND, detail="User not found")
+
+    user.ai_provider = body.ai_provider
+    user.ai_model = body.ai_model
+    session.add(user)
+    await session.flush()
+
+    return {
+        "id": str(user.id),
+        "email": user.email,
+        "ai_provider": user.ai_provider,
+        "ai_model": user.ai_model,
+    }

backend/main.py

@@ -175,4 +175,6 @@ app.include_router(settings_router)
 
 # Phase 2: auth and admin routers
 from api.auth import router as auth_router  # noqa: E402
+from api.admin import router as admin_router  # noqa: E402
 app.include_router(auth_router)
+app.include_router(admin_router)

backend/tests/test_admin_api.py

@@ -213,10 +213,19 @@ async def test_cannot_deactivate_only_admin(admin_client):
 @pytest.mark.asyncio
 async def test_password_reset_initiates_email(admin_client):
     """POST /api/admin/users/{id}/password-reset → 202; no token returned."""
+    from unittest.mock import patch
     client, _admin, session = admin_client
     target = await make_regular_user(session)
 
-    resp = await client.post(f"/api/admin/users/{target.id}/password-reset")
+    # Mock Celery task to avoid Redis connection in unit tests
+    with patch("tasks.email_tasks.send_reset_email.delay") as mock_delay:
+        resp = await client.post(f"/api/admin/users/{target.id}/password-reset")
+        # Verify email was dispatched (no return of token to caller)
+        mock_delay.assert_called_once()
+        call_args = mock_delay.call_args[0]
+        assert call_args[0] == target.email  # sent to the right address
+        assert "token=" in call_args[1]  # reset link contains token
+
     assert resp.status_code == 202
     data = resp.json()
     # No token, no impersonation — just a message