Add table gitlab_merge_request_approver (parity with github_pull_request_review)

[christoph-buente]

Summary

We use Steampipe for change-management / audit exports: merged PR/MR populations by project, branch, and date range, including who approved each change.

On GitHub (turbot/github), this works via a SQL join to github_pull_request_review (state = 'APPROVED'). On GitLab (theapsgroup/gitlab), gitlab_merge_request covers merged MR metadata, but there is no table or column for approver identity—only merged_by_username, which is not the same as approvers.

We would value MR-level approval data exposed in SQL. This is a contribution-friendly request; happy to help test on self-managed GitLab if useful.

---

What is missing (vs GitHub)

Need	GitHub (turbot/github)	GitLab plugin today
Merged changes in window	github_pull_request	gitlab_merge_request
Who approved	github_pull_request_review (author_login, state = 'APPROVED')	Not available
Join keys	repository_full_name + number	Would need project_id + iid

Insufficient substitutes on gitlab_merge_request:

• reviewers / assignees (jsonb) — assignment, not approval
• merged_by_username — who merged, not who approved
• approvals_before_merge — rule count, not usernames

---

Proposed addition

Preferred: new table gitlab_merge_request_approval (one row per approver per MR), keyed by project_id + merge_request_iid (required qualifiers, consistent with gitlab_merge_request).

Columns from Merge request approvals API — GET /projects/:id/merge_requests/:merge_request_iid/approvals:

• approver_id, approver_username, approver_name, approved_at (from approved_by[])

Alternative: approved_by jsonb (or similar) on gitlab_merge_request — simpler, weaker for joins/aggregations.

This differs from #80 (project-level approval rules), not per-MR approved_by.

---

Target SQL (after feature exists)

SELECT
  mr.iid,
  mr.merged_at,
  mr.author_username,
  mr.merged_by_username,
  STRING_AGG(DISTINCT a.approver_username, ',' ORDER BY a.approver_username) AS approved_by
FROM gitlab_merge_request mr
LEFT JOIN gitlab_merge_request_approval a
  ON a.project_id = mr.project_id AND a.merge_request_iid = mr.iid
WHERE mr.project_id = $1
  AND mr.state = 'merged'
  AND mr.merged_at BETWEEN $2 AND $3
GROUP BY 1, 2, 3, 4;

GitHub equivalent today:

LEFT JOIN github_pull_request_review rev
  ON rev.repository_full_name = pr.repository_full_name
 AND rev.number = pr.number
 AND rev.state = 'APPROVED'

---

Data is available outside Steampipe

The GitLab REST API and GitLab CLI (glab) already expose this, e.g.:

glab api "projects/<project_id>/merge_requests/<iid>/approvals"
glab mr view <iid> -R <namespace/project>

We currently enrich exports with per-MR API/glab calls. Native plugin support would avoid N+1 scripts and match our GitHub Steampipe workflow.

---

Use case

Audit and compliance workflows that require CSV (or SQL) evidence of merged changes with approver identities, not only merger and assigned reviewers—especially when exporting hundreds of MRs across many projects on a schedule.

---

Thank you for maintaining this plugin.