Add document processing api

[pahjbo]

need an api call that will convert the justifications into separate PDFs - the call should return whether the conversion runs successfully. Any files that are included in the document store are presented "in the same directory" as the main text so that inclusions (for images and possible bibliography) can also be made

• for latex a "standard style" will be assumed and the VM that the latex processing runs on will have only that style included so that attempts to use a different style will fail.

the above probably means that a "document processing" micro service needs to be created. It might be best that the front end talks to that directly so that this issue would really belong in the project that creates the micro service

[pahjbo]

this has mostly been completed for Latex - however not as separate micro service, but integrated in with the API micro service - need to be able to deploy successfully