sources/oauth: directly call AuthorizedServiceBackend instead of authenticate()

passbook/sources/oauth/auth.py

@@ -0,0 +1,23 @@
+"""passbook oauth_client Authorization backend"""
+from django.contrib.auth.backends import ModelBackend
+from django.db.models import Q
+from django.http import HttpRequest
+
+from passbook.core.models import User
+from passbook.sources.oauth.models import OAuthSource, UserOAuthSourceConnection
+
+
+class AuthorizedServiceBackend(ModelBackend):
+    "Authentication backend for users registered with remote OAuth provider."
+
+    def authenticate(
+        self, request: HttpRequest, source: OAuthSource, identifier: str
+    ) -> User:
+        "Fetch user for a given source by id."
+        source_q = Q(source__name=source)
+        if isinstance(source, OAuthSource):
+            source_q = Q(source=source)
+        access = UserOAuthSourceConnection.objects.filter(
+            source_q, identifier=identifier
+        ).select_related("user")[0]
+        return access.user