fix(invoices): say what payment detail is missing, per currency (#2126) (#2139)

"Fakturan saknar ett betalningskonto för vald valuta" read as a
foreign-currency account when the invoice was in SEK and the gap was
simply the company's bankgiro; the remediation line also asked for an
IBAN, which SEK does not need. A Visma-migrated user marking invoices
as sent hit this and went looking for a valutakonto.

- describeMissingInvoicePaymentAccount(currency) in
  lib/invoices/payment-accounts.ts: SEK names bankgiro, plusgiro, Swish
  or bank account; other currencies ask for an IBAN account in that
  currency (USD/GBP also offer routing number / sort code + BIC). Both
  point at Inställningar → Fakturering.
- getErrorMessage branches on INVOICE_SEND_PAYMENT_ACCOUNT_MISSING +
  details.currency (every dashboard route already sends it), before the
  English registry shortcut so both locales get the specific text.
- Registry entry rewritten currency-neutral for consumers without
  details (API, MCP): bankgiro/plusgiro/Swish/bankkonto for SEK, IBAN
  otherwise; remediation no longer says IBAN for everything.
- Staged-operation commit path uses the helper directly.

Tests: helper per currency, client mapping sv/en and the no-details
fallback.

Closes #2126


Claude-Session: https://claude.ai/code/session_01WFhSQWzu5SyXB6kG5ActZc

Co-authored-by: Jakob Wennberg <311770904+jakobwennberg-oss@users.noreply.github.com>
Co-authored-by: Claude Fable 5.1 <noreply@anthropic.com>

lib/invoices/__tests__/payment-accounts.test.ts

@@ -3,6 +3,8 @@ import {
   InvoicePaymentAccountMissingError,
   assertInvoicePaymentAccountForRender,
   companyWithInvoicePaymentAccount,
+  describeMissingInvoicePaymentAccount,
+  isInvoicePaymentAccountCurrency,
   hasRequiredInvoicePaymentAccount,
   hasUsableInvoicePaymentAccount,
   invoiceRequiresPaymentAccount,
@@ -212,3 +214,42 @@ describe('invoice payment accounts', () => {
     expect(hasRequiredInvoicePaymentAccount(emptySettings, makeInvoice())).toBe(false)
   })
 })
+
+describe('describeMissingInvoicePaymentAccount (#2126)', () => {
+  it('SEK: names the domestic options and never talks about currency accounts', () => {
+    const { sv, en } = describeMissingInvoicePaymentAccount('SEK')
+    expect(sv).toContain('bankgiro')
+    expect(sv).toContain('plusgiro')
+    expect(sv).toContain('Swish')
+    expect(sv).toContain('Inställningar → Fakturering')
+    expect(sv).not.toMatch(/valuta/i)
+    expect(sv).not.toMatch(/IBAN/)
+    expect(en).toContain('bankgiro')
+    expect(en).toContain('Settings → Invoicing')
+    expect(en).not.toMatch(/currency/i)
+  })
+
+  it('EUR: asks for an IBAN account in that currency', () => {
+    const { sv, en } = describeMissingInvoicePaymentAccount('EUR')
+    expect(sv).toContain('EUR')
+    expect(sv).toContain('IBAN')
+    expect(sv).not.toContain('routing number')
+    expect(sv).toContain('Inställningar → Fakturering')
+    expect(en).toContain('EUR')
+    expect(en).toContain('IBAN')
+  })
+
+  it('USD/GBP: also offers the non-IBAN routing path', () => {
+    expect(describeMissingInvoicePaymentAccount('USD').sv).toContain('routing number')
+    expect(describeMissingInvoicePaymentAccount('GBP').sv).toContain('sort code')
+    expect(describeMissingInvoicePaymentAccount('GBP').en).toContain('sort code')
+  })
+
+  it('isInvoicePaymentAccountCurrency guards the details field', () => {
+    expect(isInvoicePaymentAccountCurrency('SEK')).toBe(true)
+    expect(isInvoicePaymentAccountCurrency('NOK')).toBe(true)
+    expect(isInvoicePaymentAccountCurrency('JPY')).toBe(false)
+    expect(isInvoicePaymentAccountCurrency(undefined)).toBe(false)
+    expect(isInvoicePaymentAccountCurrency(42)).toBe(false)
+  })
+})

lib/invoices/payment-accounts.ts

@@ -141,6 +141,39 @@ export function hasRequiredInvoicePaymentAccount(
     )
 }
 
+/**
+ * What "payment account missing" means for THIS currency, in the user's
+ * words. The registry entry for INVOICE_SEND_PAYMENT_ACCOUNT_MISSING has to
+ * stay currency-neutral; on a SEK invoice its "betalningskonto för vald
+ * valuta" read as a foreign-currency account when the gap was simply the
+ * company's bankgiro (#2126). Pure: shared by the server envelopes, the
+ * staged-operation commit path and the client-side error mapper.
+ */
+export function describeMissingInvoicePaymentAccount(
+  currency: Currency,
+): { sv: string; en: string } {
+  if (currency === 'SEK') {
+    return {
+      sv: 'Fakturan saknar betalningsuppgifter: företaget har inget bankgiro, plusgiro, Swish-nummer eller bankkonto att skriva på fakturan. Lägg till ett under Inställningar → Fakturering och försök igen.',
+      en: 'The invoice has no payment details: the company has no bankgiro, plusgiro, Swish number or bank account to print on the invoice. Add one under Inställningar → Fakturering (Settings → Invoicing) and try again.',
+    }
+  }
+  const routingSv = isNonIbanCurrency(currency)
+    ? `, eller med ${currency === 'USD' ? 'routing number' : 'sort code'}, kontonummer och BIC,`
+    : ''
+  const routingEn = isNonIbanCurrency(currency)
+    ? `, or with ${currency === 'USD' ? 'routing number' : 'sort code'}, account number and BIC,`
+    : ''
+  return {
+    sv: `Fakturan är i ${currency}, men företaget saknar ett betalningskonto för ${currency}. Lägg till ett konto med IBAN${routingSv} för ${currency} under Inställningar → Fakturering och försök igen.`,
+    en: `The invoice is in ${currency}, but the company has no ${currency} payment account. Add an account with an IBAN${routingEn} for ${currency} under Inställningar → Fakturering (Settings → Invoicing) and try again.`,
+  }
+}
+
+export function isInvoicePaymentAccountCurrency(value: unknown): value is Currency {
+  return typeof value === 'string' && (INVOICE_PAYMENT_ACCOUNT_CURRENCIES as readonly string[]).includes(value)
+}
+
 export class InvoicePaymentAccountMissingError extends Error {
   readonly code = 'INVOICE_SEND_PAYMENT_ACCOUNT_MISSING'
   readonly currency: Currency