fix for german government restrictions

Hi, as mentioned in the ticket system. I am using the module in germany and wanted to send an xml invoice to a government institution. I got it back with a hint of several errors. I fixed them and now it is working. I attached created this merge request to provide the changes to all. I Tested this with PHP8.1 and Dolibarr 16.0.5. Please have a look if the changes are fine for you. Every feedback is welcomed.

Some additional information:

• Regarding the global Id I did some research and the current implementation for germany is not working. The ISO 6523 code for germany does not exists and is not accepted by the goverment systems. Also the variables idprofX doesnt contain an iso 6523 compatible global id it contains the city of the registration of the company - which means many will have the same content here and it is not unique. Therefore I created a configuration so that the global id can be skipped. With these changes the german goverment systems accepted the invoice.

Regards, Sven