Make MyPy happy

Fixes for various type errors throw by mypy.

portal/model/UtcDateTime.py

@@ -28,12 +28,12 @@ class UtcDateTime(types.TypeDecorator):
         return types.String(32)
 
     def process_bind_param(
-        self, value: Any | None, dialect: Dialect
+        self, value: datetime | None, dialect: Dialect
     ) -> Optional[str | datetime]:
-        if isinstance(value, datetime):
-            return value.astimezone(timezone.utc).isoformat()
+        if value is None:
+            return None
 
-        return None
+        return value.astimezone(timezone.utc).isoformat()
 
     def process_result_value(
         self, value: str | None, dialect: Dialect