Make dest. bic optional in simple sepa transfer

Author: yniverz

fints/client.py

@@ -811,7 +811,7 @@ def simple_sepa_transfer(self, account: SEPAAccount, iban: str, bic: str,
 
         :param account: SEPAAccount to start the transfer from.
         :param iban: Recipient's IBAN
-        :param bic: Recipient's BIC
+        :param bic: Recipient's BIC (Can be None if domestic)
         :param recipient_name: Recipient name
         :param amount: Amount as a ``Decimal``
         :param account_name: Sender account name
@@ -838,12 +838,13 @@ def simple_sepa_transfer(self, account: SEPAAccount, iban: str, bic: str,
         payment = {
             "name": recipient_name,
             "IBAN": iban,
-            "BIC": bic,
             "amount": round(Decimal(amount) * 100),  # in cents
             "execution_date": datetime.date(1999, 1, 1),
             "description": reason,
             "endtoend_id": endtoend_id,
         }
+        if bic:
+            payment["BIC"] = bic
         sepa.add_payment(payment)
         xml = sepa.export().decode()
         return self.sepa_transfer(account, xml, pain_descriptor="urn:iso:std:iso:20022:tech:xsd:"+version, instant_payment=instant_payment)