feat: add Linear destination

[PFCAaron12]

What does this PR do?

1. Add LinearDestinationConfig to drt/config/models.py

2. Create drt/destinations/linear.py

3. Register in DestinationConfig union and _get_destination() in CLI

Related Issue

Closes #37

Checklist

• Tests pass (make test)
• Linter passes (make lint)
• Updated CHANGELOG.md (if user-facing change)

[github-actions]

All contributors have signed the CLA ✍️ ✅
_{Posted by the CLA Assistant Lite bot.}

[masukai]

Thanks @PFCAaron12 — Linear is a useful destination for alerting workflows! 🙌

A few things to address:

1. PR title

Looks like the branch command ended up as the title — could you update it to something like feat: add Linear destination?

2. CI is failing

config.team_id is referenced in linear.py but LinearDestinationConfig only defines team_id_env. You'll need either a team_id field (like Discord's webhook_url / webhook_url_env pattern) or update the code to use resolve_env(None, config.team_id_env).

3. Missing CLI wiring

_get_destination() in drt/cli/main.py needs the Linear destination registered (import, type union, isinstance check). See how SendGrid was added in your other PR for reference.

4. Tests needed

Please add unit tests — tests/unit/test_discord.py is a good template to follow.

5. CLA

Please sign the CLA by posting a comment:

I have read the CLA Document and I hereby sign the CLA

6. Minor

• Missing newline at end of linear.py

Also noting that #194 (SendGrid) has similar feedback — feel free to tackle both together. Happy to help if you have questions! 🚀

[masukai]

Apologies for the delay. I’m away for a few days but will prioritize this when I’m back.

[PFCAaron12]

I have made the changes and the tests are in tests/unit/test_linear_destination.py.

[PFCAaron12]

I have read the CLA Document and I hereby sign the CLA

[masukai]

Thanks again, @PFCAaron12 — really appreciate the back-to-back contributions with SendGrid and now Linear! 🙌 Great to see you expanding drt's integration coverage.

The revised commit addresses most of the earlier feedback (PR title, CLI wiring, tests, CLA) — thank you for following up on those. The core logic (GraphQL mutation, template rendering, retry + rate limiting) looks solid.

I found a few alignment items compared to patterns that were recently refined across other destinations. Since the fixes are mostly mechanical, I'll merge this and apply them myself post-merge so you're not blocked. Listing them here for transparency:

Items I'll fix post-merge:

• Add describe() method to LinearDestinationConfig
• Fix resolve_env(config.team_id, config.team_id_env) so the team_id field is actually used
• Add on_error == "fail" break logic after error handlers
• Use sync_options.retry with _DEFAULT_RETRY fallback
• Add default=str to json.dumps() for record preview safety
• Trailing newlines, logger, CHANGELOG entry, module docstring
• Test cleanup with monkeypatch for env vars

These are all patterns refined during recent merges, so totally understandable they weren't in place here.

Merging with squash — thanks for helping expand drt's destination coverage! Linear is a great addition for engineering alerting workflows. 🎉

If you enjoy using drt, a ⭐ on the repo would mean a lot. Happy to see more PRs from you!