Add follow activity to outbox with private visibility

Introduces a call to add_to_outbox when creating a follow activity, ensuring it is added with private visibility. This helps manage the visibility of follow actions and improves activity tracking.

Author: pfefferle

includes/collection/class-following.php

@@ -88,6 +88,8 @@ public static function follow( $post, $user_id ) {
 			$follow->set_object( $post->guid );
 			$follow->set_to( array( $post->guid ) );
 
+			$id = add_to_outbox( $follow, null, $user_id, ACTIVITYPUB_CONTENT_VISIBILITY_PRIVATE );
+
 			if ( ! $id || \is_wp_error( $id ) ) {
 				return new \WP_Error( 'activitypub_follow_failed', 'Failed to add follow to outbox' );
 			}