Bugfix.
Steps to reproduce:
1. Create a fresh DB with the Brazilian localization.
2. Create a new Credit Note (directly from the menu, not from an
invoice). Confirm.
3. Observe that you get a ValidationError: "Another entry with the same
name already exists." because the name of the Credit Note is
NFe 00000001, and an invoice called NFe 00000001 already exists.
Analysis:
The credit note should be called NFe 00000002, because in Brazil the
same sequences should be used both for invoices and for credit notes of
a given document type.
However, because the `refund_sequence` field is set to True on the
'Customer Invoices' journal, the sequence mixin doesn't consider
invoices and credit notes as using the same sequence, and therefore
doesn't consider the existing invoice when finding a new name for the
credit note.
Solution:
Set the field `refund_sequence` to False on the journal created by the
l10n_br template.
We also take the opportunity to move the code that provides a default
name to the demo invoices to a separate file demo/account_demo.py, for
consistency with other localizations.
closesodoo/odoo#137700
Signed-off-by: Josse Colpaert <jco@odoo.com>