Ensure the converter can create print-ready proofs for print-on-demand jobs

[sydseter]

Is your feature request related to a problem? Please describe.

In order to drive the project further and create print ready proofs for print-on-demand we need to be able to script the idml to pdf convertion.

Describe the solution you'd like
A clear and concise description of what you want to happen.

Scribus looks promising: https://wiki.scribus.net/canvas/Command_line_scripts#Usefull_'Create_PDF_out_of_existing_scribus_document'_script

Perhaps we could create a github action for doing the convertion or a python module.

Describe alternatives you've considered

Indesign server is an alternative, but it’s a commercial product.

Additional context

Currently we are not delivering print ready design files. A designer always have install the fonts, open the idml document, clone the back of the card 79 times to the correct place and export to pdf.
Instead we should just be able to deliver final pdfs and not idml with embedded art works.

As a middle step we could look into correctly add the links to the graphics from python, but I am afraid it won’t be platform dependent.