Newsletter Settings: fix REST API bug

[arcangelini]

Fixes CML-621

Proposed changes:

• If newsletter category is not associative array ( $newsletter_category['term_id'] ) then return the value.

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

p1751296364493759-slack-C03NLNTPZ2T

Currently on Simple sites we are saving newsletter category ID's as array of objects with term_id's this is being handled in WPCOM_JSON_API_Site_Settings_Endpoint. However the Jetpack/Atomic setting is saving it as a flat array of integers in Jetpack_Core_API_Data.n This is causing a mismatch and leading the PHP warnings.

This PR will add a case to convert the array to the proper format.

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

No

Testing instructions:

1. Apply this change to an Atomic site
2. Go to Newsletter Settings page wordpress.com/settings/newsletter/[YOUR_SITE]
3. Enable the "Enable newsletter categories" toggle and check some categories
4. Save settings
5. Go to https://developer.wordpress.com/docs/api/console/
6. Query the settings from WP.COM API ⇢ v1.4 ⇢ GET ⇢ /sites/$site-slug/settings and look for wpcom_newsletter_categories in the results.

Before	After

[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 fix/newsletter-category-php-warnings branch.
• To test on Simple, run the following command on your sandbox:

bin/jetpack-downloader test jetpack fix/newsletter-category-php-warnings

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[github-actions]

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[jp-launch-control]

Code Coverage Summary

Coverage changed in 1 file.

File	Coverage	Δ%	Δ Uncovered
projects/plugins/jetpack/_inc/lib/core-api/class.jetpack-core-api-module-endpoints.php	163/891 (18.29%)	-0.52%	29 💔

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.}

[jeherve]

I wonder if we should also do some check / casting on $newsletter_category, or can we always expect it to be in the right format?