use deply for architecture checks of correct layering #34
Description
Use deply (https://pypi.org/project/deply/, or a similar tool if needed) to check that the import relationships between architectural layers contain only intended ones.
The intended layering is described in docs/internal_notes.md. (It may contain errors.)
Develop the integration on a branch (including all markup possibly required in the source files) and submit it as a single pull request.
Integrate a call in a GitHub Actions CI job.