Retain approval history for successful deployments after rules have changed

Problem

If an approval rule is deleted and a new rule is added, the new rule will appear in previously successful deployments with no option to actually approve. The previous approval from the deleted approval rule is not shown. Since the rule is deleted, we cannot show the capacity at which the previous approval was made, but the current implementation gives the appearance that an approval is still required and not completed.

This caused confusion with a GitLab Dedicated customer since they could see the approval in the audit events, but the UI did not show approvals and the users could not add any approvals.

The example below is the current behaviour after Deployment 3 had been approved and deployed using a protected environment rule that has since been deleted / recreated. The audit logs show that the deployment was approved and deployed.

Proposal

Display the previous approval history in the UI. Do not display the new approval rules for deployments that were previously approved / can't be approved anymore.