Models: Small payment fixes

Elwig/Models/PaymentMember.cs

@@ -2,7 +2,7 @@ using Microsoft.EntityFrameworkCore;
 using System.ComponentModel.DataAnnotations.Schema;
 
 namespace Elwig.Models {
-    [Table("payment_member"), PrimaryKey("Year", "AvNr", "MgNr")]
+    [Table("payment_member"), PrimaryKey("Year", "AvNr", "MgNr"), Index("Year", "TgNr", IsUnique = true)]
     public class PaymentMember {
         [Column("year")]
         public int Year { get; set; }
@@ -16,6 +16,9 @@ namespace Elwig.Models {
         [Column("amount")]
         public long AmountValue { get; set; }
 
+        [Column("tgnr")]
+        public int? TgNr { get; set; }
+
         [NotMapped]
         public decimal Amount {
             get => Variant.Season.DecFromDb(AmountValue);