 Set up secretless publishing to PyPI

This also implements sigstore signing of the artifacts.

.github/workflows/ci-cd.yml

@@ -202,9 +202,17 @@ jobs:
 
   deploy:
     name: Deploy
-    environment: release
     needs: [build-tarball, build-wheels]
     runs-on: ubuntu-latest
+
+    permissions:
+      contents: write  # IMPORTANT: mandatory for making GitHub Releases
+      id-token: write  # IMPORTANT: mandatory for trusted publishing & sigstore
+
+    environment:
+      name: pypi
+      url: https://pypi.org/p/multidict
+
     steps:
     - name: Checkout
       uses: actions/checkout@v3
@@ -220,7 +228,27 @@ jobs:
         name: multidict
         version_file: multidict/__init__.py
         github_token: ${{ secrets.GITHUB_TOKEN }}
-        pypi_token: ${{ secrets.PYPI_API_TOKEN }}
         artifact: dist
         fix_issue_regex: ":issue:`(\\d+)`"
         fix_issue_repl: "(#\\1)"
+
+    - name: >-
+        Publish 🐍📦 to PyPI
+      uses: pypa/gh-action-pypi-publish@release/v1
+
+    - name: Sign the dists with Sigstore
+      uses: sigstore/gh-action-sigstore-python@v1.2.3
+      with:
+        inputs: >-
+          ./dist/*.tar.gz
+          ./dist/*.whl
+
+    - name: Upload artifact signatures to GitHub Release
+      # Confusingly, this action also supports updating releases, not
+      # just creating them. This is what we want here, since we've manually
+      # created the release above.
+      uses: softprops/action-gh-release@v1
+      with:
+        # dist/ contains the built packages, which smoketest-artifacts/
+        # contains the signatures and certificates.
+        files: dist/**