Fix: Show error if site uses "Almost Pretty Permalink" structure (#1570)

* Fix #1282

Show an error if site uses the old "Almost Pretty Permalink" structure. We can not guarantee that the plugin works properly with that setup.

Fix #1282

* Add changelog

* improve wording

props AI

---------

Co-authored-by: Automattic Bot <[email protected]>

Author: pfefferle

.github/changelog/1570-from-description

@@ -0,0 +1,4 @@
+Significance: patch
+Type: fixed
+
+Show Site Health error if site uses old "Almost Pretty Permalinks" structure.

includes/wp-admin/class-health-check.php

@@ -432,6 +432,18 @@ public static function test_pretty_permalinks() {
 					esc_url( admin_url( 'options-permalink.php' ) )
 				)
 			);
+		} elseif ( str_starts_with( $permalink_structure, '/index.php' ) ) {
+			$result['status']         = 'critical';
+			$result['label']          = \__( 'Your permalink structure needs to be updated for ActivityPub to work properly.', 'activitypub' );
+			$result['badge']['color'] = 'red';
+			$result['description']    = \sprintf(
+				'<p>%s</p>',
+				sprintf(
+					/* translators: %s: Permalink settings URL. */
+					\__( 'Your current permalink structure includes <code>/index.php</code> which is not compatible with ActivityPub. Please <a href="%s">update your permalink settings</a> to use a standard format without <code>/index.php</code>.', 'activitypub' ),
+					esc_url( admin_url( 'options-permalink.php' ) )
+				)
+			);
 		}
 
 		return $result;