Remove GLUE_LINK_DELETE_DATA constant definition and add runtime check

- Remove hardcoded GLUE_LINK_DELETE_DATA constant definition from uninstall.php
- Add defined() check before using GLUE_LINK_DELETE_DATA constant
- Allows users to define constant in wp-config.php without default fallback
- Prevents data deletion unless explicitly enabled by user

Author: ajaydsouza

uninstall.php

@@ -10,13 +10,6 @@
 	exit;
 }
 
-/**
- * Define GLUE_LINK_DELETE_DATA as true in wp-config.php to delete all data on uninstall.
- */
-if ( ! defined( 'GLUE_LINK_DELETE_DATA' ) ) {
-	define( 'GLUE_LINK_DELETE_DATA', false );
-}
-
 /**
  * Delete options and data for a single site.
  *
@@ -39,7 +32,7 @@ function glue_link_delete_site_options( int $site_id = 0 ): void {
 		delete_option( $option_name );
 	}
 
-	if ( GLUE_LINK_DELETE_DATA ) {
+	if ( defined( 'GLUE_LINK_DELETE_DATA' ) && GLUE_LINK_DELETE_DATA ) {
 
 		// Delete the subscribers table.
 		$table_name = $wpdb->prefix . 'glue_link_subscribers';