Add admin settings update and license APIs

[syedgalib]

PR Type

What kind of change does this PR introduce?

• Bugfix
• Security fix
• Improvement
• New Feature
• Refactoring (no functional changes, no api changes)
• Build related changes
• Text changes
• Other... Please describe:

Description

Why is this PR needed?

The App Toolkit admin settings endpoint is read-only, does not expose an All Listings layout, and cannot report whether the site has a current Directorist license entitlement. Administrators need to update app configuration through the API, while clients need a boolean entitlement state.

What is done in this PR?

• Adds authenticated partial POST, PUT, and PATCH updates to /directorist-app-toolkit/v1/admin-settings.
• Adds the app_layout_all_listings JSON setting.
• Activates the first valid Directorist EDD entitlement after successful Themes & Extensions authentication and stores a normalized site-wide state without persisting the raw license key.
• Adds the boolean has_active_license field to admin settings responses.
• Validates settings before saving and rejects unknown, read-only, or invalid JSON values.

How to test the PR

1. Log in as an administrator and send a partial PATCH request to /wp-json/directorist-app-toolkit/v1/admin-settings; confirm only submitted values change and the full settings object is returned.
2. Update app_layout_all_listings with a JSON object and confirm GET returns the decoded object; confirm invalid JSON, unknown fields, and has_active_license updates return 400.
3. Repeat the update unauthenticated and confirm it is rejected.
4. Log in to Directorist through Themes & Extensions with an account containing valid licenses, then confirm the first valid license is activated and GET returns has_active_license: true.
5. Confirm an expired or unavailable entitlement returns has_active_license: false.

Task Links

• https://docs.google.com/document/d/1KhKZS_l0GDTBtgPkFrLISeBVuN2i-gj1ykC9UzlOG7k/edit?tab=t.0