feat: allow to create empty pi via email append to

[blaggacao]

Prior

• Not possible:
  

Now

• Possible

Note

This is better than to create a simple ToDo or Communication in the case that a IMAP folder is guaranteed (or almost guaranteed) to only receive emails (through successful sender hygiene), because:

• It is clear what to do next
• Automation (e.g. XML parser) can built upon this to automatically parse a machine readable invoice
• ToDos are only seen by System Managers (or by assignee or assigner), however this is not useful for incoming Invoices, nor is it useful to open up permissions as ToDos are inherently personal
• Communication is too general as a doctype
• ...

no-docs

[blaggacao]

@barredterra potentially a necessary change to start automating parsing of incoming (per mail) e invoices.