User.handle_as: handle web users with custom usernames

bug fix for b255962, fixes https://console.cloud.google.com/errors/detail/CPiAj72alvDYNQ;time=P30D?project=bridgy-federated

models.py

@@ -322,8 +322,11 @@ class User(StringIdModel, metaclass=ProtocolUserMeta):
         if isinstance(to_proto, str):
             to_proto = PROTOCOLS[to_proto]
 
-        return ids.translate_handle(handle=self.handle, from_proto=self.__class__,
-                                  to_proto=to_proto)
+        # override web users to always use domain instead of custom username
+        handle = self.key.id() if self.LABEL == 'web' else self.handle
+
+        return ids.translate_handle(handle=handle, from_proto=self.__class__,
+                                    to_proto=to_proto)
 
     def id_as(self, to_proto):
         """Returns this user's id in a different protocol.

tests/test_models.py

@@ -158,6 +158,14 @@ class UserTest(TestCase):
         self.assertEqual('fake:handle:user', user.handle_as('fake'))
         self.assertEqual('@fake:handle:user@fa.brid.gy', user.handle_as('ap'))
 
+    def test_handle_as_web_custom_username(self, *_):
+        self.user.obj.our_as1 = {
+            'objectType': 'person',
+            'url': 'acct:alice@y.z',
+        }
+        self.assertEqual('alice', self.user.username())
+        self.assertEqual('@y.z@web.brid.gy', self.user.handle_as('ap'))
+
     @patch('requests.get', return_value=requests_response(DID_DOC))
     def test_ap_actor(self, mock_get):
         user = self.make_user('did:plc:abc', cls=ATProto)