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/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