Post by Email abilities: register status read + regenerate-address via Registrar

[enejb]

Summary

Adds two abilities for the Post by Email module via the standard wp-abilities/v1 REST surface, mirroring the Monitor abilities pattern.

• jetpack-post-by-email/get-status — per-user read of { active, address, address_active, last_used_at }. address is null when the user has not enabled PBE; last_used_at is reserved (always null in this release) since the remote service does not currently expose last-used metadata.
• jetpack-post-by-email/regenerate-address — rotates the user's address; annotated readonly=false, destructive=true (invalidates the previous address — saved drafts pointing at it will no longer reach the site), idempotent=false (each call mints a new address).

Both abilities are gated on is_user_logged_in() — Post by Email is a per-user feature; the remote service uses the caller's Jetpack user token, so users cannot view or rotate anyone else's address.

Implementation

• Post_By_Email_Abilities extends Registrar, lives at projects/plugins/jetpack/modules/post-by-email/abilities/class-post-by-email-abilities.php (Case A — module-colocated).
• Wired from modules/post-by-email.php, so abilities only register while the Post by Email module is active (load_modules() only includes the module file when it's on).
• Protected seams (is_user_connected_to_jetpack, fetch_address, apply_regenerate) allow tests to drive both happy paths and remote-failure paths without a Jetpack token fixture or live IXR endpoint.
• Precondition and transport failures surface as WP_Error with the shared jetpack_post_by_email_* vocabulary so callers (agents) get an actionable next step rather than opaque nulls.
• Mirrors the post-rotate response to the legacy post_by_email_address{user_id} option so Jetpack_Core_Json_Api_Endpoints::get_remote_value stays in sync.

Test plan

• CI: Post_By_Email_Abilities_Test passes — Registrar wiring (gate filter, lifecycle hooks, per-ability allow-list, category auto-injection), permission callbacks, execute callbacks (module-inactive, not-connected, happy paths, service-unreachable, non-idempotency across calls), and the activation-gating bootstrap assertion.
• On a connected WP 6.9+ site with the jetpack_wp_abilities_enabled filter true and the Post by Email module active, confirm /wp-json/wp-abilities/v1/abilities lists jetpack-post-by-email/get-status and jetpack-post-by-email/regenerate-address, and get-status returns the documented shape.
• Deactivate the Post by Email module and confirm the two slugs disappear from wp_get_abilities().

Local phpunit could not run in this environment (the host's phpunit-select-config shim is not on PATH outside Docker) — relying on CI.

Plan reference: §3.3 (Post by Email).

[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/ship-post-by-email-abilities branch.
• To test on Simple, run the following command on your sandbox:

bin/jetpack-downloader test jetpack add/ship-post-by-email-abilities

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]

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[jp-launch-control]

Code Coverage Summary

Cannot generate coverage summary while tests are failing. 🤐

Please fix the tests, or re-run the Code coverage job if it was something being flaky.

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