Formsetname and formfieldname must be unique in one transaction with two files. #101
Description
When you create a transaction with two documents and a metadata formset per document (https://evidos.github.io/api/howto/2016/10/06/api-generated-fields.html)
the formfield ID and formset ID have to be unique, even across two different metadata documents. Otherwise the transaction ends up 'in progress' and cannot be completed.
Advise to reflect this requirement in the documentation: Formset name and forfield names have to be unique in a transaction.
