IAddress: Add IAddress

Elwig/Helpers/IAddress.cs

@@ -0,0 +1,9 @@
+using Elwig.Models;
+
+namespace Elwig.Helpers {
+    public interface IAddress {
+        string Name { get; }
+        string Address { get; }
+        PostalDest PostalDest { get; }
+    }
+}

Elwig/Models/BillingAddr.cs

@@ -1,9 +1,10 @@
+using Elwig.Helpers;
 using Microsoft.EntityFrameworkCore;
 using System.ComponentModel.DataAnnotations.Schema;
 
 namespace Elwig.Models {
     [Table("member_billing_address"), PrimaryKey("MgNr")]
-    public class BillingAddr {
+    public class BillingAddr : IAddress {
         [Column("mgnr")]
         public int MgNr { get; set; }
 

Elwig/Models/Member.cs

@@ -7,7 +7,7 @@ using System.Linq;
 
 namespace Elwig.Models {
     [Table("member"), PrimaryKey("MgNr")]
-    public class Member {
+    public class Member : IAddress {
         [Column("mgnr")]
         public int MgNr { get; set; }