Merge branch 'main' into glitch-soc/merge-upstream

Conflicts:
- `.github/workflows/build-image.yml`:
  Upstream changed how docker images were built, including how
  they were cached.
  I don't know much about it, so applied upstream's changes.
- `app/controllers/admin/domain_blocks_controller.rb`:
  The feature, that was in glitch-soc, got backported upstream.
  It also had a few fixes upstream, so those have been ported!
- `app/javascript/packs/admin.js`:
  Glitch-soc changes have been backported upstream. As a result,
  some code from `app/javascript/core/admin.js` got added upstream.
  Kept our version since our shared Javascript already has that feature.
- `app/models/user.rb`:
  Upstream added something to distinguish unusable and unusable-because-moved
  accounts, while glitch-soc considers moved accounts usable.
  Took upstream's code for `functional_or_moved?` and made `functional?`
  call it.
- `app/views/statuses/_simple_status.html.haml`:
  Upstream cleaned up code style a bit, on a line that we had custom changes
  for.
  Applied upstream's change while keeping our change.
- `config/initializers/content_security_policy.rb`:
  Upstream adopted one CSP directive we already had.
  The conflict is because of our files being structurally different, but the
  change itself was already part of glitch-soc.
  Kept our version.

app/serializers/manifest_serializer.rb

@@ -35,6 +35,7 @@ class ManifestSerializer < ActiveModel::Serializer
         src: full_pack_url("media/icons/android-chrome-#{size}x#{size}.png"),
         sizes: "#{size}x#{size}",
         type: 'image/png',
+        purpose: 'any maskable',
       }
     end
   end