Add polygon to DTO convert strategy

StructureHelperCommon/Models/Shapes/IPolygonLineSegment.cs

@@ -0,0 +1,15 @@
+using System;
+using System.Collections.Generic;
+using System.Linq;
+using System.Text;
+using System.Threading.Tasks;
+
+namespace StructureHelperCommon.Models.Shapes
+{
+    /// <summary>
+    /// Implements line segment of polygon
+    /// </summary>
+    internal interface IPolygonLineSegment : IPolygonSegment
+    {
+    }
+}