Display when an invoice is paid on the report
It is a common request that the invoice report shows the status paid when it is paid. The problem is that we store a copy of the generated document when posted (so it is never paid at this moment) because we need to ensure to always print the same invoice after that. So the idea is to use watermark that is added on the fly on the stored (or not) document. For that we need that the document is in PDF so we can use the PyPDF2 tools to merge pages. Also the watermark is also a report to render like that it can be customized and translated. With this feature we could also add a watermark when it is a draft invoice.