#7610187 Theme Subscriptions: Add third-party theme options to the theme kebab menu

Proposed Changes

This adds third-party theme options to the theme kebab menu.

NOTE: At this time, checking out/subscribing isn’t implemented. This functionality will be added later after we’ve made the appropriate backend updates.

Testing Instructions

To test, you’ll need to simulate a third-party theme by adding the following to 0-sandbox.php on your sandbox, then sandboxing public-api.wordpress.com.

function test_theme_type( $theme ) {
	if ( $theme['id'] === 'varese' ) {
		$theme['theme_type'] = 'managed-external';
	}

	return $theme;
}

add_filter( 'wpcom_theme_api_meta', 'test_theme_type', 1000 );

Testing a Free site

• The simulated third-party theme should say “Upgrade to subscribe”
  

• Bundled themes should say “Upgrade to activate”
  

• Regular premium themes should say “Purchase”
  

• Free themes should say “Activate”
  

Testing a Business plan site

• The simulated third-party theme should say “Subscribe”
  

All other theme types should read as described above.

Pre-merge Checklist

• Have you written new tests for your changes?
• Have you tested the feature in Simple (P9HQHe-k8-p2), Atomic (P9HQHe-jW-p2), and self-hosted Jetpack sites (PCYsg-g6b-p2)?
• Have you checked for TypeScript, React or other console errors?
• Have you used memoizing on expensive computations? More info in Memoizing with create-selector and Using memoizing selectors and Our Approach to Data
• Have we added the “[Status] String Freeze” label as soon as any new strings were ready for translation (p4TIVU-5Jq-p2)?

Related to #69470