[#17] CreditNote: Overhaul CreditNote

Elwig/Documents/CreditNote.cs

@@ -5,6 +5,7 @@ using Elwig.Models.Entities;
 namespace Elwig.Documents {
     public class CreditNote : BusinessDocument {
 
+        public PaymentMember? Payment;
         public Credit? Credit;
         public CreditNoteData Data;
         public string? Text;
@@ -16,6 +17,7 @@ namespace Elwig.Documents {
             UseBillingAddress = true;
             ShowDateAndLocation = true;
             Data = data;
+            Payment = p;
             Credit = p.Credit;
             Aside = Aside.Replace("</table>", "") +
                 $"<thead><tr><th colspan='2'>Gutschrift</th></tr></thead><tbody>" +