ci: publish to pypi and sign packages

Based on
https://packaging.python.org/en/latest/guides/publishing-package-distribution-releases-using-github-actions-ci-cd-workflows/

Author: iMichka

.github/workflows/tests.yml

@@ -3,10 +3,7 @@ on:
     branches:
       - master
       - develop
-  release:
-    types: [created]
   pull_request:
-  workflow_dispatch:
 
 jobs:
   tests:
@@ -245,9 +242,9 @@ jobs:
           export PATH=~/castxml/bin:$PATH
           pytest tests
 
-  build-release:
+  build:
     name: Build distribution 📦
-    if: (github.event_name == 'release' && github.event.action == 'created') || (github.event_name == 'workflow_dispatch')
+    if: startsWith(github.ref, 'refs/tags/')  # only publish to PyPI on tag pushes
     needs: tests
     runs-on: ubuntu-latest
 
@@ -273,3 +270,69 @@ jobs:
       with:
         name: python-package-distributions
         path: dist/
+
+  publish-to-pypi:
+    name: >-
+      Publish Python 🐍 distribution 📦 to PyPI
+    if: startsWith(github.ref, 'refs/tags/')  # only publish to PyPI on tag pushes
+    needs:
+    - build
+    runs-on: ubuntu-latest
+    environment:
+      name: pypi
+      url: https://pypi.org/p/<package-name>  # Replace <package-name> with your PyPI project name
+    permissions:
+      id-token: write  # IMPORTANT: mandatory for trusted publishing
+
+    steps:
+    - name: Download all the dists
+      uses: actions/download-artifact@v4
+      with:
+        name: python-package-distributions
+        path: dist/
+    - name: Publish distribution 📦 to PyPI
+      uses: pypa/gh-action-pypi-publish@release/v1
+
+  github-release:
+    name: >-
+      Sign the Python 🐍 distribution 📦 with Sigstore
+      and upload them to GitHub Release
+    if: startsWith(github.ref, 'refs/tags/')  # only publish to PyPI on tag pushes
+    needs:
+    - publish-to-pypi
+    runs-on: ubuntu-latest
+
+    permissions:
+      contents: write  # IMPORTANT: mandatory for making GitHub Releases
+      id-token: write  # IMPORTANT: mandatory for sigstore
+
+    steps:
+    - name: Download all the dists
+      uses: actions/download-artifact@v4
+      with:
+        name: python-package-distributions
+        path: dist/
+    - name: Sign the dists with Sigstore
+      uses: sigstore/[email protected]
+      with:
+        inputs: >-
+          ./dist/*.tar.gz
+          ./dist/*.whl
+    - name: Create GitHub Release
+      env:
+        GITHUB_TOKEN: ${{ github.token }}
+      run: >-
+        gh release create
+        "$GITHUB_REF_NAME"
+        --repo "$GITHUB_REPOSITORY"
+        --notes ""
+    - name: Upload artifact signatures to GitHub Release
+      env:
+        GITHUB_TOKEN: ${{ github.token }}
+      # Upload to GitHub Release using the `gh` CLI.
+      # `dist/` contains the built packages, and the
+      # sigstore-produced signatures and certificates.
+      run: >-
+        gh release upload
+        "$GITHUB_REF_NAME" dist/**
+        --repo "$GITHUB_REPOSITORY"