Resolve "Improve the security via HTTP headers"

Closes #880

See merge request funkwhale/funkwhale!826

Semantic to fomentic

See merge request funkwhale/funkwhale!831

Needed for CSP, and also helps with redusing JS size ;)

See #432: API for tags

See merge request funkwhale/funkwhale!830

See #432: added model tagging logic on artists and albums

See merge request funkwhale/funkwhale!829

Increase the security of JWT token generation by using DJANGO_SECRET_KEY as...

See merge request funkwhale/funkwhale!828

Increase the security of JWT token generation by using DJANGO_SECRET_KEY as well as user-specific salt for the signature

See #432: tags acquisition (from audio files)

See merge request funkwhale/funkwhale!822

See #432: API endpoints to query tags

See merge request funkwhale/funkwhale!824

See #432: expose and reuse tags over federation

See merge request funkwhale/funkwhale!823

Fix #875 Broken embed (develop)

Closes #875

See merge request funkwhale/funkwhale!825

Fixed a typo in Contributing links

See merge request funkwhale/funkwhale!827

Improve Docker installation documentation

See merge request funkwhale/funkwhale!810

- Use `useradd` features to simplify user creation:
  - `-U` creates a user group,
  - `-G docker` adds the user to the `docker` group
- Document available versions and their usage
- Use `chmod 0600` before editing the file!
- Use `cat` instead of multiple `echo`es
- Comment all lines in `.env`
- Use `${FUNKWHALE_VERSION}` where applicable instead of `|version|` to
enable copy-pasting more commands

Implement tag models

See merge request funkwhale/funkwhale!814