Merge branch '1288-user-me-can-be-created-but-cannot-be-edited' into 'develop'

Draft: Use proper RegisterSerializer

Closes #1288

See merge request funkwhale/funkwhale!1398

api/funkwhale_api/cli/users.py

@@ -36,6 +36,7 @@ def handler_create_user(
     )
     utils.logger.debug("Validating user data…")
     serializer.is_valid(raise_exception=True)
+    serializer.validate_username(username)
 
     # Override e-mail validation, we assume accounts created from CLI have a valid e-mail
     request = FakeRequest(session={"account_verified_email": email})