Make sure caseworking users clear their invite

There was a bug where caseworking users skipped the part of the invite
flow where their invite was cleared from the session. This caused
a 500 if they later tried to create another service.

This commit makes sure that both types of user have the invite cleared
from the session after accepting it.

tests/conftest.py

@@ -2597,7 +2597,13 @@ def os_environ():
 
 
 @pytest.fixture
-def client_request(logged_in_client):
+def client_request(
+    logged_in_client,
+    active_user_with_permissions,
+    mocker,
+    service_one,
+    fake_uuid,
+):
     class ClientRequest:
 
         @staticmethod
@@ -2606,6 +2612,9 @@ def client_request(logged_in_client):
             with logged_in_client.session_transaction() as session:
                 yield session
 
+        def login(user, service=service_one):
+            logged_in_client.login(user, mocker, service)
+
         @staticmethod
         def get(
             endpoint,