use hashid for serialization

app/models.py

@@ -271,7 +271,7 @@ class Avatar(HashidMixin, FileMixin, db.Model):
 
     def to_json_serializeable(self, backrefs=False, relationships=False):
         json_serializeable = {
-            'id': self.id,
+            'id': self.hashid,
             **self.file_mixin_to_json_serializeable()
         }
         return json_serializeable