Forms: Add form response webhooks

[vianasw]

Proposed changes:

This PR adds the basic form webhook functionality to allow users to integrate with external services.

• Webhook Configuration UI: Added webhook settings panel in the Jetpack Forms block editor sidebar with:
  • Toggle to enable/disable webhooks
  • Webhook ID input field for unique webhook identification
  • Webhook URL input field for the external endpoint
  • Feature gated behind jetpack_forms_webhooks_enabled filter (default: false)
• Webhook Processing: Form submissions now trigger POST requests to configured webhook URLs with:
  • JSON format support (properly encoded as JSON string, not URL-encoded)
  • Form submission data sent as payload
  • Webhook responses logged to post meta for debugging/tracking
  • jetpack_forms_before_webhook_request filter to allow modification of data before sending (parameters: webhook_id, form_data)
• Data Structure: Webhook configuration stored in block attributes as array supporting:
  • webhook_id: unique identifier
  • url: endpoint URL
  • format: 'json' (default, hardcoded for now)
  • method: 'POST' (default, hardcoded for now)
  • enabled: boolean toggle

Other information:

• Have you written new tests for your changes, if applicable?
• Have you checked the E2E test CI results, and verified that your changes do not break them?
• Have you tested your changes on WordPress.com, if applicable (if so, you'll see a generated comment below with a script to run)?

Jetpack product discussion

Does this pull request change what data or activity we track or use?

Testing instructions:

• Enable webhooks via the filter flag:

  add_filter( 'jetpack_forms_webhooks_enabled', '__return_true' );

• Create a form with webhook configuration in the block editor
• Enter a webhook URL (e.g., https://webhook.site/unique-url for testing)
  • Publish/update the post and submit the form
  • Verify the webhook endpoint receives the form data in JSON format
  • Check the feedback CPT post meta for _jetpack_forms_webhook_response to see logged responses
• Verify that without the filter flag enabled, webhooks are not initialized even if configured in the form

[github-actions]

Are you an Automattician? Please test your changes on all WordPress.com environments to help mitigate accidental explosions.

• To test on WoA, go to the Plugins menu on a WoA dev site. Click on the "Upload" button and follow the upgrade flow to be able to upload, install, and activate the Jetpack Beta plugin. Once the plugin is active, go to Jetpack > Jetpack Beta, select your plugin (Jetpack), and enable the add/form-response-webhooks branch.
• To test on Simple, run the following command on your sandbox:

bin/jetpack-downloader test jetpack add/form-response-webhooks

Interested in more tips and information?

• In your local development environment, use the jetpack rsync command to sync your changes to a WoA dev blog.
• Read more about our development workflow here: PCYsg-eg0-p2
• Figure out when your changes will be shipped to customers here: PCYsg-eg5-p2

[github-actions]

Thank you for your PR!

When contributing to Jetpack, we have a few suggestions that can help us test and review your patch:

• ✅ Include a description of your PR changes.
  
• ✅ Add a "[Status]" label (In Progress, Needs Review, ...).
  
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• ✅ Add testing instructions.
  
• ✅ Specify whether this PR includes any changes to data or privacy.
  
• ✅ Add changelog entries to affected projects
  

This comment will be updated as you work on your PR and make changes. If you think that some of those checks are not needed for your PR, please explain why you think so. Thanks for cooperation 🤖

---

Follow this PR Review Process:

1. Ensure all required checks appearing at the bottom of this PR are passing.
2. Make sure to test your changes on all platforms that it applies to. You're responsible for the quality of the code you ship.
3. You can use GitHub's Reviewers functionality to request a review.
4. When it's reviewed and merged, you will be pinged in Slack to deploy the changes to WordPress.com simple once the build is done.

If you have questions about anything, reach out in #jetpack-developers for guidance!

---

Jetpack plugin:

The Jetpack plugin has different release cadences depending on the platform:

• WordPress.com Simple releases happen as soon as you deploy your changes after merging this PR (PCYsg-Jjm-p2).
• WoA releases happen weekly.
• Releases to self-hosted sites happen monthly:
  • Scheduled release: December 2, 2025

If you have any questions about the release process, please ask in the #jetpack-releases channel on Slack.

[jp-launch-control]

Code Coverage Summary

Coverage changed in 5 files.

File	Coverage	Δ%	Δ Uncovered
projects/packages/forms/src/contact-form/class-contact-form-plugin.php	461/1365 (33.77%)	-0.20%	12 💔
projects/packages/forms/src/blocks/contact-form/edit.tsx	0/272 (0.00%)	0.00%	1 ❤️‍🩹
projects/packages/forms/src/class-jetpack-forms.php	6/17 (35.29%)	4.04%	0 💚
projects/packages/forms/src/contact-form/class-contact-form-endpoint.php	775/906 (85.54%)	0.02%	0 💚
projects/packages/forms/src/contact-form/class-contact-form.php	894/1296 (68.98%)	0.02%	0 💚

2 files are newly checked for coverage.

File	Coverage
projects/packages/forms/src/blocks/contact-form/components/webhooks-settings.js	0/23 (0.00%) 💔
projects/packages/forms/src/service/class-form-webhooks.php	88/89 (98.88%) 💚

Full summary · PHP report · JS report

_{If appropriate, add one of these labels to override the failing coverage check: Covered by non-unit tests Use to ignore the Code coverage requirement check when E2Es or other non-unit tests cover the code Coverage tests to be added later Use to ignore the Code coverage requirement check when tests will be added in a follow-up PR I don't care about code coverage for this PR Use this label to ignore the check for insufficient code coveage.}