Working on users view, added infrastructure lib

UserService.Infrastructure/DataModels/Member.cs

@@ -0,0 +1,13 @@
+using System.Collections.Generic;
+using System.ComponentModel.DataAnnotations;
+
+namespace UserService.Infrastructure.DataModels
+{
+    public abstract class Member : Node
+    {
+        [EmailAddress]
+        public string? EMail { get; set; }
+
+        public ICollection<UserMember> Members { get; set; } = new List<UserMember>();
+    }
+}