sources/oauth: fix UserOAuthSourceConnection not being assigned to user after enrollment

sources/oauth: separate handle_new_connection into handle_existing_user_link and handle_enroll

passbook/sources/oauth/views/flows.py

@@ -0,0 +1,28 @@
+"""OAuth Stages"""
+from django.http import HttpRequest, HttpResponse
+
+from passbook.audit.models import Event, EventAction
+from passbook.core.models import User
+from passbook.flows.planner import PLAN_CONTEXT_PENDING_USER
+from passbook.flows.stage import StageView
+from passbook.sources.oauth.models import UserOAuthSourceConnection
+
+PLAN_CONTEXT_SOURCES_OAUTH_ACCESS = "sources_oauth_access"
+
+
+class PostUserEnrollmentStage(StageView):
+    """Dynamically injected stage which saves the OAuth Connection after
+    the user has been enrolled."""
+
+    def get(self, request: HttpRequest, *args, **kwargs) -> HttpResponse:
+        access: UserOAuthSourceConnection = self.executor.plan.context[
+            PLAN_CONTEXT_SOURCES_OAUTH_ACCESS
+        ]
+        user: User = self.executor.plan.context[PLAN_CONTEXT_PENDING_USER]
+        access.user = user
+        access.save()
+        UserOAuthSourceConnection.objects.filter(pk=access.pk).update(user=user)
+        Event.new(
+            EventAction.CUSTOM, message="Linked OAuth Source", source=access.source
+        ).from_http(self.request)
+        return self.executor.stage_ok()