Add Custom Role Permission to Override API-Based MR Approval Rule Restrictions
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### Proposal
This feature proposes adding a new permission to the [Custom Roles](https://docs.gitlab.com/user/custom_roles/) feature in GitLab that allows designated users to bypass the [prevent editing approval rules in merge requests](https://docs.gitlab.com/user/project/merge_requests/approvals/settings/#prevent-editing-approval-rules-in-merge-requests) restriction while keeping it enabled globally.
Currently, when the prevent editing approval rules in merge requests setting is enabled at the project or group level, it blocks all modifications to approval rules for existing merge requests through both the UI and API by returning a `403`.
For the specific customer this proposal is created on behalf of, this would allow them to be able to maintain this restriction while at the same time allow the injecting of specific approval rules on-demand.
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