chore(models): convert created_by_role to its value for consistency (#9612)

api/models/model.py

@@ -1109,7 +1109,7 @@ class MessageFile(db.Model):
         self.url = url
         self.belongs_to = belongs_to
         self.upload_file_id = upload_file_id
-        self.created_by_role = created_by_role
+        self.created_by_role = created_by_role.value
         self.created_by = created_by
 
     id: Mapped[str] = db.Column(StringUUID, server_default=db.text("uuid_generate_v4()"))