feat(thread_replies): Add module to handle own Twitter thread replies

[klausi]

Fixes #34

[bajtos]

Awesome improvement, @klausi.

It makes me wonder how is this going to interact with deleting old tweets.

In my experience, most of the time I execute mastodon-twitter-sync, it deletes only subset of tweets to avoid hitting rate limit. Could it happen that when we abort cleanup early, we end up with a partially-deleted thread that will be handled incorrectly by the next sync?

I guess this depends on the cleanup algorithm. If it deletes threads from the most-recent post to the oldest one, then all should be good. However, if we delete from the oldest tweets, then we may delete the "parent" tweet but keep "child" replies around?

[klausi]

Yes, we could end up with partially deleted threads. Child posts would stay around until they are old enough to be deleted. I think that is a bit ugly but should not be a problem otherwise.

I think I'm almost finished here, just had some problems during testing where Twitter attachments are used. I will look into that a bit and then this can be merged I think.