Fleshed out the table storage service and started syncing logic

Habitica.Todoist.Integration.Model/Storage/TodoHabitLink.cs

@@ -1,12 +1,26 @@
-using System;
+using Microsoft.Azure.Cosmos.Table;
+using System;
 using System.Collections.Generic;
 using System.Text;
 
 namespace Habitica.Todoist.Integration.Model.Storage
 {
-    public class TodoHabitLink
+    public class TodoHabitLink : TableEntity
     {
-        public string TodoistId { get; set; }
+        public TodoHabitLink() { }
+
+        public TodoHabitLink(string userId, string todoistId, string habiticaId)
+        {
+            PartitionKey = userId;
+            RowKey = todoistId;
+            HabiticaId = habiticaId;
+        }
+
         public string HabiticaId { get; set; }
+
+        public HabitTodoLink Reverse()
+        {
+            return new HabitTodoLink(PartitionKey, HabiticaId, RowKey);
+        }
     }
 }