Approval Gate from External System on merge requests to PROD deploy branch

Here at Radford University, we are required to have electronic approval on code deployed to Production.

I’m wondering if anyone has configured that sort of thing in GitLab as an “approval gate” on merge requests. Can the GitLab-EE merge request approvers feature be configured for a specific list of approvers based on the target branch for all Projects created in a Group? Maybe folks do this with a third party CI system?

We use an issue tracking system called ServiceNow which we may need to use for the approvals. That would mean making an api call from GitLab when a merge request is created to start the ServiceNow approval process which seems easy enough… Is there a mechanism available in GitLab to accept that back again. Perhaps the Jira or Redmine intergration provides a model for this?

I’m hoping for some guidance on where to look to clone the functionality if it exists, or suggestions on how others might be accomplishing this sort of approval step.

Did you manage to resolve this? I am looking to implement this type of approval process for Prod. I would like to hear of your experiences and lessons learnt. If you have the time to share.
Iain