Issue helpers

Issue helpers

• Fortnox error: 2004344 - Kunde inte hämta/hitta valuta.
• InvoiceUnderPayment(20007014, InvalidData)
• InvoiceOverPayment(20007013, InvalidData)
• CurrencyMismatch: Currencies Currency(NOK) and Currency(SEK) don't match
• Fortnox error: 2001339
• Fortnox error: 2000946