Local PlantUML support

[DatBlaueHus]

We should support compilation to PlantUML for the use in MkDocs, so that we can have data driven diagrams in our documentation.

Using the server is not the best method, as it always sends (potentially sensitive) customer information to a server.

https://github.com/quantorconsulting/mkdocs_build_plantuml

[github-actions]

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