apply_filters( 'authenticate', null|WP_User|WP_Error $user, string $username, string $password )

700		 *701		 * @param null|WP_User|WP_Error $user     WP_User if the user is authenticated.702		 *                                        WP_Error or null otherwise.703		 * @param string                $username Username or email address.704		 * @param string                $password User password.705		 */706		$user = apply_filters( 'authenticate', null, $username, $password );707 708		if ( null === $user || false === $user ) {709			/*710			 * TODO: What should the error message be? (Or would these even happen?)711			 * Only needed if all authentication handlers fail to return anything.712			 */