Refactored AgeGroup namespace and services, added RegistrationKey functionality.

API/Models/Internal/User/RegistrationKey.cs

@@ -0,0 +1,24 @@
+namespace API.Models.Internal.User;
+
+public class RegistrationKey
+{
+    public string Id { get; set; } = Ulid.NewUlid().ToString();
+    public string? LinkedRole { get; set; }
+    public DateTime Created { get; set; } = DateTime.UtcNow;
+}
+
+public class RegistrationKeyIngoing
+{
+    public string? LinkedRole { get; set; }
+}
+
+public static class RegistrationKeyMapper
+{
+    public static RegistrationKey ToInternalFromIngoing(this RegistrationKeyIngoing key)
+    {
+        return new RegistrationKey
+        {
+            LinkedRole = key.LinkedRole,
+        };
+    }
+}