ci: automate releases with release-plz

.github/workflows/release-plz.yml

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+name: Release-plz
+
+on:
+  push:
+    branches:
+      - main
+  workflow_dispatch:
+
+permissions:
+  contents: read
+
+jobs:
+  release-plz-pr:
+    name: Release-plz PR
+    # Don't run on forks.
+    if: github.repository == 'aws/aws-lambda-web-adapter'
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+      pull-requests: write
+    concurrency:
+      group: release-plz-${{ github.ref }}
+      cancel-in-progress: false
+    steps:
+      - name: Generate a GitHub App token
+        uses: actions/create-github-app-token@v3
+        id: app-token
+        with:
+          app-id: ${{ secrets.RELEASE_PLZ_APP_ID }}
+          private-key: ${{ secrets.RELEASE_PLZ_APP_PRIVATE_KEY }}
+      - name: Checkout repository
+        uses: actions/checkout@v6
+        with:
+          fetch-depth: 0
+          persist-credentials: false
+          token: ${{ steps.app-token.outputs.token }}
+      - name: Install Rust toolchain
+        uses: dtolnay/rust-toolchain@stable
+      - name: Run release-plz (release-pr)
+        uses: release-plz/action@v0.5
+        with:
+          command: release-pr
+        env:
+          GITHUB_TOKEN: ${{ steps.app-token.outputs.token }}
+
+  release-plz-release:
+    name: Release-plz release
+    if: github.repository == 'aws/aws-lambda-web-adapter'
+    runs-on: ubuntu-latest
+    permissions:
+      contents: write
+      pull-requests: write
+      id-token: write # crates.io trusted publishing (OIDC)
+    steps:
+      - name: Generate a GitHub App token
+        uses: actions/create-github-app-token@v3
+        id: app-token
+        with:
+          app-id: ${{ secrets.RELEASE_PLZ_APP_ID }}
+          private-key: ${{ secrets.RELEASE_PLZ_APP_PRIVATE_KEY }}
+      - name: Checkout repository
+        uses: actions/checkout@v6
+        with:
+          fetch-depth: 0
+          persist-credentials: false
+          token: ${{ steps.app-token.outputs.token }}
+      - name: Install Rust toolchain
+        uses: dtolnay/rust-toolchain@stable
+      - name: Run release-plz (release)
+        uses: release-plz/action@v0.5
+        with:
+          command: release
+        env:
+          GITHUB_TOKEN: ${{ steps.app-token.outputs.token }}

release-plz.toml

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+[workspace]
+# Reuse the existing git-cliff config so the changelog keeps its current style.
+changelog_config = "cliff.toml"
+
+# Match the existing tag scheme (v1.0.1, ...) so version detection works and the
+# tags stay compatible with release.yaml / the SAM templates.
+git_tag_name = "v{{ version }}"
+git_tag_enable = true
+
+# Create the GitHub Release as a full PUBLISHED release (not a draft), so that
+# release.yaml's `on: release: types: [released]` trigger fires.
+git_release_enable = true
+git_release_draft = false
+
+# Only cut a release when the Release PR is merged, not on every push to `main`.
+release_always = false
+
+# Publish lambda_web_adapter to crates.io.
+# Auth is provided by crates.io trusted publishing (OIDC) in release-plz.yml.
+publish = true