Feat/podcast guid

Features

• 🔑 Add guid to podcasts, for more information, see https://github.com/Podcastindex-org/podcast-namespace/blob/main/docs/1.0.md#guid

Update Instructions

1. Run the following .sql script on your database:

SET AUTOCOMMIT = 0;
START TRANSACTION;

/* Add GUID to podcasts */
ALTER TABLE `cp_podcasts` ADD `guid` CHAR(36) NULL AFTER `id`;
UPDATE `cp_podcasts` SET `guid`=UUID();
ALTER TABLE `cp_podcasts` CHANGE `guid` `guid` CHAR(36) NOT NULL;
ALTER TABLE `cp_podcasts` ADD UNIQUE `guid` (`guid`); 

COMMIT;

Regarding your existing podcasts on Castopod, please note that this mysql-generated guid will perfectly work but will not follow exactly the PodcastIndex guidelines (if you want a v5 UUID with the podcast namespace you should calculate it and manually update it in the database). On the other hand, all uuids generated on new or imported podcasts will follow the PodcastIndex specification.