GitLab integration: post comments on linked issues and MRs

[emyller]

Context: #7000

When a feature flag is linked to a GitLab issue or MR (#7160), Flagsmith should post a comment showing the flag's current state across all environments. When the flag state changes or the flag is deleted, a new comment should be posted automatically.

Scope

• Post to issues via POST /api/v4/projects/:id/issues/:iid/notes.
• Post to MRs via POST /api/v4/projects/:id/merge_requests/:iid/notes.
• Trigger on: flag linked, flag state changed, flag deleted.

Note

PR #7122 contains an async task (post_gitlab_comment) and dispatch function (dispatch_gitlab_comment) that can be used as a starting point. A few things to consider:

• The PR extracts GitHub's generate_body_comment into a shared integrations/vcs/comments.py module. This refactors integrations/github/github.py. generate_body_comment currently has no tests — they need to be added.
• Incomplete per author: the hooks that auto-trigger comments are not done. The GitHub integration calls call_github_task from six places across features/models.py, features/serializers.py, features/versioning/serializers.py, and features/feature_external_resources/models.py. The GitLab equivalent of these hooks is new work.

Acceptance criteria

• Comment posted to GitLab when a flag is linked to an issue or MR
• Comment posted when the linked flag's state changes in any environment
• Comment posted when the linked flag is deleted
• Comment generation logic is tested
• Emit structlog events for product telemetry (Epic: Open structured event pipeline for the backend #7012)

[SahilJat]

Hey @emyller ! I'd love to take this on, but I see it depends on PR #7122. Can you assign this to me, and I'll start working on it as soon as that PR is merged?

[emyller]

Hey @emyller ! I'd love to take this on, but I see it depends on PR #7122. Can you assign this to me, and I'll start working on it as soon as that PR is merged?

Hey @SahilJat, thanks for making yourself available! This issue is part of a larger effort we're still planning / experimenting with. We might already have some work to push here. 😉