Also this: https://itunespartner.apple.com/en/podcasts/faq/Getting%20Started_Podcast%20Basics#76672088 Do I need to use HTTPS on my hosting server? iTunes supports and will eventually require HTTPS protocol for servers hosting your content and metadata.
The only thing you need to do to 'support' this is use the current protocol when constructing links and enclosures. All items load over SSL; they simply need to be referenced correctly. https://developers.google.com/web/fundamentals/security/encrypt-in-transit/why-https