CREATE TABLE IF NOT EXISTS platform_admins (
  user_id INT PRIMARY KEY,
  granted_by_user_id INT NULL,
  created_at DATETIME NOT NULL DEFAULT CURRENT_TIMESTAMP,
  CONSTRAINT fk_platform_admins_user
    FOREIGN KEY (user_id) REFERENCES users(id)
    ON DELETE CASCADE,
  CONSTRAINT fk_platform_admins_granted_by
    FOREIGN KEY (granted_by_user_id) REFERENCES users(id)
    ON DELETE SET NULL
) ENGINE=InnoDB DEFAULT CHARSET=utf8mb4 COLLATE=utf8mb4_unicode_ci;