Models: Small payment fixes

Elwig/Models/Season.cs

@@ -48,6 +48,12 @@ namespace Elwig.Models {
         [InverseProperty("Season")]
         public virtual ISet<Modifier> Modifiers { get; private set; }
 
+        [InverseProperty("Season")]
+        public virtual ISet<PaymentVar> PaymentVariants { get; private set; }
+
+        [InverseProperty("Season")]
+        public virtual ISet<Delivery> Deliveries { get; private set; }
+
         public decimal DecFromDb(long value) {
             return Utils.DecFromDb(value, Precision);
         }