Add RubyGems trusted publishing workflow

Author: arukaen

.github/workflows/release.yml

@@ -0,0 +1,30 @@
+name: Release
+
+on:
+  push:
+    tags:
+      - 'v*'
+
+permissions:
+  contents: read
+
+jobs:
+  publish:
+    name: Publish to RubyGems
+    runs-on: ubuntu-latest
+    environment: release
+    permissions:
+      contents: write
+      id-token: write
+    steps:
+      - name: Checkout
+        uses: actions/checkout@v7
+        with:
+          persist-credentials: false
+      - name: Set up Ruby
+        uses: ruby/setup-ruby@v1
+        with:
+          ruby-version: '3.3'
+          bundler-cache: true
+      - name: Release gem
+        uses: rubygems/release-gem@v1

README.md

@@ -61,3 +61,21 @@ $ sudo env PATH="$PATH" GEM_HOME="$GEM_HOME" GEM_PATH="$GEM_PATH" \
 
 Regenerate the unit with `--force` after a Ruby upgrade. See
 [docs/systemd.md](docs/systemd.md) for the full guide.
+
+## Release
+
+Releases use RubyGems [trusted publishing](https://guides.rubygems.org/trusted-publishing) —
+no API tokens. The trusted publisher must be registered for this repo and the
+`release.yml` workflow on RubyGems.org (a pending publisher becomes a normal
+one after its first push). To release:
+
+1. Bump the version in `passenger_datadog.gemspec` and add a `CHANGELOG.md` entry.
+2. Commit, tag, and push:
+
+```
+$ git tag v2.0.0
+$ git push origin v2.0.0
+```
+
+`.github/workflows/release.yml` builds the gem and pushes it to RubyGems.org,
+authenticating with an OIDC token scoped to this gem.

Rakefile

@@ -4,6 +4,7 @@ require 'rake'
 require 'rspec/core'
 require 'rspec/core/rake_task'
 require 'rubocop/rake_task'
+require 'bundler/gem_tasks'
 
 RSpec::Core::RakeTask.new(:spec)