Conflicts:
- `app/serializers/rest/instance_serializer.rb`:
Upstream changed the fields returned by /api/v1/instance by adding a
`configuration` field holding a lot of useful information making our
`max_toot_chars` and `poll_limits` fields obsolete.
Keeping those around for now for compatibility.
- `app/validators/status_length_validator.rb`:
No real conflict, just URL_PLACEHOLDER_CHARS introduced too close to
MAX_CHARS which is defined differently in glitch-soc.
Ported upstream changes.
cdf20f4367