Creating and deploying a release

We now use lots of fancy automated release processes in this repository. Releasing should be as easy as making a semver release on GH, with the desired version. This will trigger a GH action to update the version in the source code, regenerate the OpenAPI schema, generate an automatic changelog and push all this to master and release to PyPI.

If desired, release notes can be added to the changelog by creating an issue with the label release-summary, and add it to a milestone that matches the tag name for the release. The issue body will then be added to the start of the changelog.