Extend invoice creation with json deserialization

[phermsdorf]

This pull request add JSON serialization and deserialization support for the following members of the Item class:

• BuyerOrderReferencedDocumentLineID
• Allowances
• Charges

I extended the DeSerializationTest to verify the changes and show the usage.

[jstaerk]

not sure about BuyerOrderReferencedDocumentLineID but I already did charges/allowances (sorry), could you please check and resolve? thanks and apologies.

[phermsdorf]

Hi @jstaerk ,

i have seen you did charges and allowances for the invoice, my change/extension is for the item.

I could revert the name change of addReferencedLineID to setBuyerOrderReferencedDocumentLineID and just add the set method if that would be better.

Should i update my pull request to the current code with that changes in place?

Thansk, Bye Peter

[jstaerk]

No matter what you do we need to at least stay compatible to the old public methods (and properties) or this has to wait for the next major version (maybe in a couple of years). e.g. public Item addReferencedLineID vs
setBuyerOrderReferencedDocumentLineID(String s) but also regards charges vs ItemCharges: actually I never tested that you have a chance that it never worked so far in which case you could of course decide for a name