Make MyPy happy

Fixes for various type errors throw by mypy.

portal/model/UtcDateTime.py

@@ -28,15 +28,15 @@ class UtcDateTime(types.TypeDecorator):
         return types.String(32)
 
     def process_bind_param(
-        self, value: datetime, dialect: Dialect
-    ) -> Optional[str | datetime]:
+        self, value: Optional[datetime], dialect: Dialect
+    ) -> Optional[str]:
         if value is None:
             return None
 
         return value.astimezone(timezone.utc).isoformat()
 
     def process_result_value(
-        self, value: str | datetime, dialect: Dialect
+        self, value: Optional[str], dialect: Dialect
     ) -> Optional[datetime]:
         if value is None:
             return None