Incomplete checklists in merge request should block approval

As requested by customer:

I'd like to define a checklist for merge requests that an approver has to go through and check off before being able to approve a merge request.

Enforce all checklists tasks are complete before allowing Merge Request approval.

Create a default Merge Request template with a checklist created in Markdown. This way, all new Merge Requests include the checklist.
Consider adding dedicated Merge Request Approvers who must approve the MR before it can be merged, and they can verify the checklist.
Custom git hooks
Disable merge requests unless discussions are resolved followed by adding the tasklist to a new discussion.

Only allow merge request approval once all items in checklist have been completed.

Prohibit merge request approval until all checklist items are complete.

To ensure workflow is consistent

Merge requests being approved without all items being actioned.

Option box in Project Settings.

Applicable to any customer who wants to enforce checklist completion.

Make sure these are completed before closing the issue, with a link to the relevant commit.