Fleshed out the table storage service and started syncing logic

Habitica.Todoist.Integration.Model/Storage/HabitTodoLink.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 HabitTodoLink
+    public class HabitTodoLink : TableEntity
     {
-        public string HabiticaId { get; set; }
+        public HabitTodoLink() { }
+
+        public HabitTodoLink(string userId, string habiticaId, string todoistId)
+        {
+            PartitionKey = userId;
+            RowKey = habiticaId;
+            TodoistId = todoistId;
+        }
+
         public string TodoistId { get; set; }
+
+        public TodoHabitLink Reverse()
+        {
+            return new TodoHabitLink(PartitionKey, TodoistId, RowKey);
+        }
     }
 }