FR: Global/default automatic-download setting

[caiw]

I've discovered one can control auto-downloading on a per-feed basis. I'd love a global/default setting so I could be sure to always download all episodes as they are released.

I like to archive podcasts I like on a Mac Mini home server. For me this is particularly relevant to e.g. Patreon feeds where I can't rely on having access to the original feed forever.

For my purposes, this relates to #99 since when adding a new podcast I want to straightaway download all episodes currently available.