/*
 * Get web-based MusicBrainz CD-ROM submission URL for CD-ROM device associated with this MusicBrainz::Client object.
 *
 * Use MusicBrainz::Client#device to set the CD-ROM device. Returns nil
 * on error.
 *
 * Aliases:
 *   MusicBrainz::Client#get_url
 *   MusicBrainz::Client#get_web_submit_url
 *
 * Examples:
 *   url = mb.url
 *   url = mb.get_url
 *   url = mb.get_web_submit_url
 *
 */
static VALUE mb_client_url(VALUE self) {