Prototype and document a PDF generation example using Jinja2, print CSS and Wesyprint

Often we need to generate PDF documents e.g reports, invoices. These are often large documents that have an effect post the generation e.g emailing a link or attaching it to a message.

The genera process is these jobs to be queued and then for a processor to collate the contents, convert it into a template which is then turned into a PDF. We have typically used [Wesayprint](https://weasyprint.org) which is a Python based tool to generate PDFs from HTML and CSS. It has deep roots where the maintainers are members of the CSS working group.

We should prototype:
- A template being processed using Jinja2
- CSS defined for print may be using a framework like [Gutenberg](https://github.com/BafS/Gutenberg)
- Sample to include, images, code
- Generate the PDF
- Store the document in an object store
- Write the link back into a database for the rest of the application to find the document

> Anomaly should also consider financially supporting Weasyprint