Add/Fix Mastodon endpoints for 2.4.3 compatibility

This is to be able to rebase mastofe on 2.4.3 and earlier releases and be sure that everything is working.

Below is the current status of pleroma before this MR, with tasks done and yet to do in this MR marked.

---

Missing

Pre-2.3.x

• Hashtag streaming, works by getting only the string in the tag field. There seems to be an issue with fixing tags in the transmogrifier as it’s putting different types in the same field.
• delete event in the user stream

2.4.3

• keyword filtering
  • /api/v1/filters GET & POST
  • /api/v1/filters/:id GET, PUT, DELETE
  • filters_changed event in the user stream
  • expiration

Faking/Ignoring

2.4.0

• profile fields
• bot account?
• custom emoji in bio/display_name, see !265 (merged)
• language code in status; currently ignored, it doesn’t supports multi-languages so it’ll stay like that

2.4.1

• Trends; I’ll probably leave it faked, so consider it done.

Done

2.4.0

• Direct Message Column
• Media Timeline

2.4.1

• /api/v2/search

Yet to be merged

2.4.3

• suggestions https://git.pleroma.social/pleroma/pleroma/merge_requests/254