Implement HandleEpisodeAction

[TheBlusky]

I figured out GET /api/2/episodes/(username).json was not implemented.

I had to add relvacode/iso8601 dependencie in order to parse the since argument (time.RFC3339 is not compatible)

Hope I did everything the way you would have done it :-)

[TheBlusky]

After using this branch on dalily basis, there is a bug with antenna pud trying to retrieve episodes.

(It sends since=0 which isn't an iso8601 date format. I'll work on that. In the mean time, don't merge it yet :-)

[oxtyped]

Thanks for working on this! 🙇

[gilcu3]

@TheBlusky is there any progress on this? As far I can see the only thing missing is a corner case in the timestamp parsing? I can help if necessary.

@oxtyped Can devices currently synchronize episode actions without this PR? Sorry if it is a silly question.

[mhrivnak]

@TheBlusky any interest in finishing this? I may be interested in helping if that would be useful.

The since argument is odd. The API docs define it as an int, even though the POST API defines timestamp as A UTC timestamp ... in ISO 8601 format

So by a strict reading of the API, I think antennapod is correct in sending a 0, even though that seems weird.

[TheBlusky]

@mhrivnak Sorry, I ended up stopping using gpodder2go. I won't finish this PR. It's more than a year old, maybe it has been implemented in main branch since ?