Implement FacturX/XRechnung/ZUGFeRD for upcoming obligation to issue and receive electronic invoices

[bastolino]

Feature Request

As already asked by https://github.com/Dolibarr/dolibarr/issues/8836 FacturX/XRechnung is a european standard (EU-Richtlinie 2014/55/EU / EN 16931) and being enforced between companies from 2025 on, it is growing a basic feature that'd rule out the usage of Dolibarr in Germany from 2027 on. It is expectable that it is going to be mandatory for other european countries aswell.

It should be possible to import invoices from FacturX aswell as import format for supplier invoices.

Use case

all companies in germany need this from 2027 on.

Suggested implementation

some hints have already been made regarding libraries.

Suggested steps

xml embedded in pdf for export, xml aswell as pdf w/ embedded xml for import