feat: add SendGrid destination

[PFCAaron12]

What does this PR do?

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

2. Create drt/destinations/sendgrid.py

3. Register the new config in DestinationConfig union in models.py

4. Wire it in drt/cli/main.py _get_destination()

5. Add tests in tests/unit/test_sendgrid.py using a FakeSendGridDestination

Related Issue

Closes #36

Checklist

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

[github-actions]

All contributors have signed the CLA ✍️ ✅
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[masukai]

Thanks for the contribution @PFCAaron12! 🙌

A SendGrid destination is a great addition. I have a few items that need to be addressed before we can merge:

1. Config model is incomplete

SendGridDestinationConfig is missing fields that the implementation relies on: from_email, from_name, subject_template, body_template, list_ids. Currently the code uses hasattr() / getattr() to check for them at runtime, but drt uses Pydantic models as the source of truth — all fields should be declared explicitly.

See how DiscordDestinationConfig handles this in drt/config/models.py for reference.

2. Tests don't exercise the real implementation

FakeSendGridDestination overrides load() entirely, so the actual SendGridDestination.load() is never called. Tests should mock httpx.Client (like tests/unit/test_discord.py does) rather than replacing the destination class.

3. CLA

Please sign the CLA by posting a comment:

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

4. Minor

• Missing newline at end of sendgrid.py and test_sendgrid.py

Happy to answer any questions — looking forward to the next revision! 🚀

[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.

[PFCAaron12]

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

[masukai]

Thanks for the quick revisions, @PFCAaron12 — and for submitting both this and #195! Really appreciate you helping expand drt's destination coverage at this early stage. 🙌

The config model rewrite and test improvements are solid — much better than the first version.

A few things I noticed that I'll clean up post-merge (no action needed from your side):

• Import sorting — ruff check --fix will sort these automatically. Tip: running make fmt locally before pushing catches these.
• Trailing newline at end of files — most editors can add this automatically (e.g., VS Code: files.insertFinalNewline)
• resolve_env() helper — the codebase has a shared helper for resolving auth tokens from env vars (drt/config/credentials.py). I'll swap in the standard pattern.
• auth field type — I'll narrow it to BearerAuth for fail-fast validation, and a few other minor consistency tweaks.

Merging with squash — thanks again for the contribution! 🎉

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