Submits a new payment default entry. Upon successful creation, the payment default ID is returned, which can be used to retrieve or update the payment default.

At least one contact method is required: either an email address or a full postal address (street, city, country, and postalCode). Up to 4 email addresses, 4 phone numbers, and 4 IBAN bank account numbers can be provided. Notices are sent to every contact address provided. Phone (SMS) is an additional notification channel.

A 422 Unprocessable Entity error is returned if:
- subjectCode fails personal identification code or registration code validation or is missing.
- contractNo exceeds 50 characters or is missing.
- beginDate is missing, not in YYYY-MM-DD format, is less than 38 days, or is earlier than 15 years ago.
- debtSum is missing, less than 30.00, or greater than 999999.99.
- bankAccountNumbers contains an invalid IBAN.
- referenceNumber is invalid.
- debtorContactDetails is missing or incomplete (no email or post address provided).
- A duplicate payment default - when already exists with the same subjectCode, beginDate, and contractNo.