bug fix and documentation

src/bulk_action.php

@@ -6,16 +6,6 @@ if ($_SERVER['REQUEST_METHOD'] === 'POST') {
     $db = getDbInstance();
     $json = json_decode(file_get_contents('php://input'), true);
 
-    if (isset($json['action'])) {
-        $action = filter_var($json['action'], FILTER_SANITIZE_FULL_SPECIAL_CHARS);
-    } else {
-        echo json_encode([
-            'data' => 'Missing action field in the request.',
-            'status' => 400
-        ]);
-        exit();
-    }
-
     $params = $json['params'];
     $files = [];