Refactor database initialization and remove Alembic migrations

- Removed legacy Alembic migration files and consolidated schema management into a new Pydantic-backed initializer (`scripts/init_db.py`).
- Updated `main.py` to ensure the new DB initializer runs on startup, maintaining idempotency.
- Adjusted session management in `config/database.py` to prevent DetachedInstanceError.
- Introduced new enums in `models/enums.py` for better organization and clarity.
- Refactored various models to utilize the new enums, improving code maintainability.
- Enhanced middleware to handle JSON validation more robustly, ensuring non-JSON requests do not trigger JSON errors.
- Added tests for middleware and enums to ensure expected behavior and consistency.
- Updated changelog to reflect significant changes and improvements.

middleware/auth_session.py

@@ -8,6 +8,7 @@ from starlette.middleware.base import BaseHTTPMiddleware, RequestResponseEndpoin
 from starlette.types import ASGIApp
 
 from config.settings import Settings, get_settings
+from sqlalchemy.orm.exc import DetachedInstanceError
 from models import User
 from monitoring.metrics import ACTIVE_CONNECTIONS
 from services.exceptions import EntityNotFoundError
@@ -66,21 +67,42 @@ class AuthSessionMiddleware(BaseHTTPMiddleware):
         resolved = self._resolve_session(request)
 
         # Track active sessions for authenticated users
-        if resolved.session.user and resolved.session.user.is_active:
+        try:
+            user_active = bool(resolved.session.user and getattr(
+                resolved.session.user, "is_active", False))
+        except DetachedInstanceError:
+            user_active = False
+
+        if user_active:
             AuthSessionMiddleware._active_sessions += 1
             ACTIVE_CONNECTIONS.set(AuthSessionMiddleware._active_sessions)
 
+        response: Response | None = None
         try:
             response = await call_next(request)
             return response
         finally:
-            # Decrement on response
-            if resolved.session.user and resolved.session.user.is_active:
+            # Always decrement the active sessions counter if we incremented it.
+            if user_active:
                 AuthSessionMiddleware._active_sessions = max(
                     0, AuthSessionMiddleware._active_sessions - 1)
                 ACTIVE_CONNECTIONS.set(AuthSessionMiddleware._active_sessions)
 
-            self._apply_session(response, resolved)
+            # Only apply session cookies if a response was produced by downstream
+            # application. If an exception occurred before a response was created
+            # we avoid raising another error here.
+            import logging
+            if response is not None:
+                try:
+                    self._apply_session(response, resolved)
+                except Exception:
+                    logging.getLogger(__name__).exception(
+                        "Failed to apply session cookies to response"
+                    )
+            else:
+                logging.getLogger(__name__).debug(
+                    "AuthSessionMiddleware: no response produced by downstream app (response is None)"
+                )
 
     def _resolve_session(self, request: Request) -> _ResolutionResult:
         settings = self._settings_provider()

middleware/validation.py

@@ -10,10 +10,14 @@ async def validate_json(
 ) -> Response:
     # Only validate JSON for requests with a body
     if request.method in ("POST", "PUT", "PATCH"):
-        try:
-            # attempt to parse json body
-            await request.json()
-        except Exception:
-            raise HTTPException(status_code=400, detail="Invalid JSON payload")
+        # Only attempt JSON parsing when the client indicates a JSON content type.
+        content_type = (request.headers.get("content-type") or "").lower()
+        if "json" in content_type:
+            try:
+                # attempt to parse json body
+                await request.json()
+            except Exception:
+                raise HTTPException(
+                    status_code=400, detail="Invalid JSON payload")
     response = await call_next(request)
     return response