#911 added self-billing fields to the shared CreateInvoiceSchema with
external_invoice_number: z.string().min(1), but the invoice form has
always sent that field (plus self_billing_agreement_ref and
received_date) as '' on every normal invoice. The empty string failed
min(1), so every invoice create returned 400.
Normalise the empty optional self-billing strings to undefined in the
schema (matching the existing optionalIsoDate / deduction_brf_org_number
patterns), and strip the unused empty carriers client-side before the
form POSTs. Required-when-self-billed is still enforced post-parse in the
v1 route, so the self-billed path is unaffected. Adds schema regression
tests.
Co-authored-by: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
Mattsson
cbffcd7292