[WIP] New user can now accept invite and will be made to

register. On succesful register and verfication they
will be added to service and forwarded to dashboard.

Nothing is done yet with the permissions requested in the
invite to the user.

tests/conftest.py

@@ -572,7 +572,7 @@ def sample_invite(mocker, service_one):
     email_address = 'invited_user@test.gov.uk'
     service_id = service_one['id']
     permissions = 'send_messages,manage_service,manage_api_keys'
-    created_at = datetime.datetime.now()
+    created_at = str(datetime.datetime.now())
     return invite_json(id, from_user, service_id, email_address, permissions, created_at)