Such payloads are generated when a GitLab repository has merge
request approvals enabled and a project member approves a merge
request. Approving is not the same as merging.
Payloads that don't have a payload['object_attributes']['action']
attribute are generated when GitLab sends a test payload to verify
if the webhook was set up successfully. In this case, we should
send a message notifying that the webhook was configured
successfully.
All webhook fixtures in zerver/fixtures/<webhook_name> have now
been moved to dedicated webhook-specific directories under
zerver/webhooks/<webhook_name>/fixtures, where <webhook_name> is
the name of the webhook.
Eeshan Garg