Billing: Update EBICS exporter

Elwig/Models/Dtos/Transaction.cs

@@ -0,0 +1,26 @@
+using Elwig.Models.Entities;
+using System.Collections.Generic;
+using System.Linq;
+
+namespace Elwig.Models.Dtos {
+    public class Transaction(Member member, decimal amount, string currency, int nr) {
+
+        public readonly Member Member = member;
+        public readonly decimal Amount = amount;
+        public readonly string Currency = currency;
+        public readonly int Nr = nr;
+
+        public Transaction(Credit c) : this(c.Member, c.Amount, c.Variant.Season.CurrencyCode, c.TgNr) { }
+
+        public static IEnumerable<Transaction> FromPaymentVariant(PaymentVar variant) {
+            return variant.Credits
+                .OrderBy(c => c.TgNr)
+                .Select(c => new Transaction(c))
+                .ToList();
+        }
+
+        public static string FormatAmountCent(long cents) => $"{cents / 100}.{cents % 100:00}";
+
+        public static string FormatAmount(decimal amount) => FormatAmountCent((int)(amount * 100));
+    }
+}