fix(firestore-send-email) restore headers support

[Nushio]

I just noticed that this feature was removed, and wanted to contribute a quick fix.

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[Nushio]

I've signed the CLA

[Copilot]

Pull Request Overview

This PR restores support for custom email headers in the Firestore email sending extension by reintroducing the missing headers field and updating documentation accordingly.

• Restores the headers property in the mail options in index.ts.
• Bumps the extension version to 0.2.4 in extension.yaml.
• Updates documentation and changelog to reflect this new feature.

Reviewed Changes

Copilot reviewed 4 out of 4 changed files in this pull request and generated no comments.

File	Description
firestore-send-email/functions/src/index.ts	Adds the headers field to email payload to support custom headers.
firestore-send-email/extension.yaml	Updates the extension version.
firestore-send-email/README.md	Adds a section on using custom headers with example JSON.
firestore-send-email/CHANGELOG.md	Documents the addition of the headers field and updates the version.

[cabljac]

Hi, can you run npm run generate-readme in the firestore-send-email/functions directory

[Nushio]

I ran it but it removes the blurb I wrote about using Custom Headers.

Where should I place that instead? PREINSTALL.md ?

Edit: Done

[Nushio]

Any blockers on this PR?

[cabljac]

Hi! No blockers, just finding time to prioritise it. Sorry for the wait.

[Nushio]

Thanks, no problem. Just wondering if there was something else missing on my end.

[CorieW]

LGTM and works fine

Just needs conflicts resolved

[Nushio]

Thank you! I'll work on these tomorrow morning!

[Nushio]

@CorieW If I did things right, it should be mergeable now.

I used version 0.2.5 as it was the next number in the list.

[cabljac]

Hi! lgtm, i'll try and get this released this week.

[CorieW]

Closing to make some minor adjustments before release in #2463

Thank you for your PR!

[Nushio]

Super discouraging, but alright. :-/

[cabljac]

Apologies @Nushio, this was miscommunication on my part. I'll see what I can do about ensuring some attribution is recognised

[cabljac]

Hi @Nushio I've created a PR to correctly attribute you:

#2471

Apologies again, your contribution is very appreciated!

[Nushio]

Thank you!

[CorieW]

Sorry about this, @Nushio

I hope this experience doesn't discourage you. We really appreciate your contributions and want to support and encourage all contributors.

Once again, thank you for your work on this!