ci(release): upgrade v*.next.forgejo.org when the release is ready

The https://v$major.next.forgejo.org instances are polling for new
releases with a cron job every hour. This is not only a waste of
resources because there is nothing most of the time, it also imposes a
delay of maximum one hour when there is a new release.

When the release is published, notify the corresponding instance that
an upgrade is ready. In the request will 404 but leave a trace in the
logs which can trigger an upgrade script if wakeup-on-logs is
configured accordingly.

  GET https://v$major.next.forgejo.org/.well-known/wakeup-on-logs/forgejo-v$major

* v8 - a daemon watching on the web server logs was installed for
  https://v8.next.forgejo.org and will perform the upgrade.
* v7 - nothing will happen for https://v7.next.forgejo.org because
  it still relies on the hourly cron job.
* v1.21 - nothing will happen because https://v1.next.forgejo.org does
  not exist.

See also:

* https://forgejo.org/docs/next/developer/infrastructure
* https://code.forgejo.org/infrastructure/wakeup-on-logs

.forgejo/workflows/publish-release.yml

@@ -59,6 +59,16 @@ jobs:
           gpg-passphrase: ${{ secrets.GPG_PASSPHRASE }}
           verbose: ${{ vars.VERBOSE }}
 
+      - name: upgrade v*.next.forgejo.org
+        run: |
+          export DEBIAN_FRONTEND=noninteractive
+          apt-get update -qq
+          apt-get -q install -y -qq curl
+          version="${{ github.ref_name }}"
+          version=${version##*v}
+          major=$(echo $version | sed -E -e 's/^([0-9]+).*/\1/')
+          # https://forgejo.org/docs/next/developer/infrastructure
+          curl -o /dev/null -sS https://v$major.next.forgejo.org/.well-known/wakeup-on-logs/forgejo-v$major
 
       - name: set up go for the DNS update below
         if: vars.ROLE == 'forgejo-experimental' && secrets.OVH_APP_KEY != ''