Tracking DB schema changes

[abitrolly]

• use https://github.com/fschulze/sqlalchemy_schemadisplay/ to generate DB schema in .png
  • make sure the .png is reproducible
  • create .png diff and return non-zero code if changes are detected
  • release new version Actions workflow to release the package fschulze/sqlalchemy_schemadisplay#30
    • test release process on tag
      • test release process by uploading to temp PyPI server
        • build PyPI server docker image
  • teach build to mention that packages are created in dist/ subdir
    • get back color to build output (main: disable colorama on Linux and flush output pypa/build#494)
• wrap DB schema dump into GitHub action