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

Conflicts:
- `.github/workflows/build-image.yml`:
  Upstream entirely refactored this, while we changed the docker repository
  to upload to and disabled the “latest” tag.
  Applied the repository change to `.github/workflows/build-*.yml`, as well
  as disabling native ARMv64 builds.
- `README.md`:
  We have a completely different README.
  Kept ours.
- `app/views/admin/settings/shared/_links.html.haml`:
  Upstream refactored, we had an extra item.
  Refactored as upstream did.
- `spec/controllers/api/v1/timelines/public_controller_spec.rb`:
  Upstream deleted this file, to be replaced by a request spec at
  `spec/requests/api/v1/timelines/public_spec.rb`.
  We had an extra bit about enabling the public timelines because we have
  different defaults than upstream.
  Moved that bit to `spec/requests/api/v1/timelines/public_spec.rb`

.github/workflows/build-push-pr.yml

@@ -0,0 +1,41 @@
+name: Build container image for PR
+on:
+  pull_request:
+    types: [labeled, synchronize, reopened, ready_for_review, opened]
+
+permissions:
+  contents: read
+  packages: write
+
+jobs:
+  compute-suffix:
+    runs-on: ubuntu-latest
+    # This is only allowed to run if:
+    # - the PR branch is in the `mastodon/mastodon` repository
+    # - the PR is not a draft
+    # - the PR has the "build-image" label
+    if: ${{ github.event.pull_request.head.repo.full_name == github.repository && !github.event.pull_request.draft && contains(github.event.pull_request.labels.*.name, 'build-image') }}
+    steps:
+      # Repository needs to be cloned so `git rev-parse` below works
+      - name: Clone repository
+        uses: actions/checkout@v3
+      - id: version_vars
+        run: |
+          echo mastodon_version_suffix=+pr-${{ github.event.pull_request.number }}-$(git rev-parse --short HEAD) >> $GITHUB_OUTPUT
+    outputs:
+      suffix: ${{ steps.version_vars.outputs.mastodon_version_suffix }}
+
+  build-image:
+    needs: compute-suffix
+    uses: ./.github/workflows/build-container-image.yml
+    with:
+      platforms: linux/amd64,linux/arm64
+      use_native_arm64_builder: false
+      push_to_images: |
+        ghcr.io/${{ github.repository_owner }}/mastodon
+      version_suffix: ${{ needs.compute-suffix.outputs.suffix }}
+      flavor: |
+        latest=auto
+      tags: |
+        type=ref,event=pr
+    secrets: inherit