feat: refuse database testing after installation

changelogs/unreleased.md

@@ -22,4 +22,4 @@
 
 ### Security
 
--   Nothing
+-   Added a check to disable database testing (`/index.php?page=api&module=database-test`) after wishthis has been installed - Thanks [@kumitterer](https://github.com/kumitterer)!

src/api/database-test.php

@@ -10,6 +10,14 @@ namespace wishthis;
 
 global $page, $database;
 
+if (isset($database) && $database) {
+    echo __('Refused to test database connection after installation.');
+
+    $response['dbTestSuccess'] = false;
+
+    return;
+}
+
 switch ($_SERVER['REQUEST_METHOD']) {
     case 'POST':
         $success = false;