Use Matador without a Redirect URI for Bullhorn

matador_variable_api_redirect_uri_set_null.php

/**
 * Authorize Matador without a Redirect URI set
 *
 * Recommended to use this only in development mode or while waiting for Bullhorn to set a 
 * new redirect URI for your API user. Letting Matador check the redirect URI is an essential 
 * safety check for your software.
 */
add_filter( 'matador_variable_api_redirect_uri', '__return_false' );