Add support for returning sync token values after committing transactions.

src/Todoist.Net.Tests/Services/TransactionTests.cs

@@ -30,11 +30,12 @@ public void CreateProjectAndCreateNote_Success()
             var note = new Note("Demo note");
             transaction.Notes.AddToProjectAsync(note, projectId).Wait();
 
-            transaction.CommitAsync().Wait();
+            var syncToken = transaction.CommitAsync().Result;
 
             var projectInfo = client.Projects.GetAsync(project.Id).Result;
 
             Assert.True(projectInfo.Notes.Count > 0);
+            Assert.NotNull(syncToken);
 
             var deleteTransaction = client.CreateTransaction();
 

src/Todoist.Net/IAdvancedTodoistClient.cs

@@ -1,4 +1,4 @@
-using System.Collections.Generic;
+using System.Collections.Generic;
 using System.Net.Http;
 using System.Threading.Tasks;
 
@@ -12,11 +12,14 @@ internal interface IAdvancedTodoistClient : ITodoistClient
         /// Executes the commands asynchronous.
         /// </summary>
         /// <param name="commands">The commands.</param>
-        /// <returns>Returns <see cref="T:System.Threading.Tasks.Task" />.The task object representing the asynchronous operation.</returns>
+        /// <returns>
+        /// Returns <see cref="Task{TResult}" />. The task object representing the asynchronous operation
+        /// that at completion returns the commands execution sync_token.
+        /// </returns>
         /// <exception cref="System.ArgumentNullException">Value cannot be null - commands.</exception>
         /// <exception cref="System.AggregateException">Command execution exception.</exception>
         /// <exception cref="HttpRequestException">API exception.</exception>
-        Task ExecuteCommandsAsync(params Command[] commands);
+        Task<string> ExecuteCommandsAsync(params Command[] commands);
 
         /// <summary>
         /// Posts the request asynchronous.

src/Todoist.Net/Models/SyncResponse.cs

@@ -12,5 +12,8 @@ internal class SyncResponse
 
         [JsonProperty("temp_id_mapping")]
         public Dictionary<Guid, string> TempIdMappings { get; set; }
+
+        [JsonProperty("sync_token")]
+        public string SyncToken { get; set; }
     }
 }

src/Todoist.Net/Services/ITransaction.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Net.Http;
 using System.Threading.Tasks;
 
@@ -70,9 +70,12 @@ public interface ITransaction
         /// <summary>
         /// Commits the transaction asynchronous.
         /// </summary>
-        /// <returns>Returns <see cref="T:System.Threading.Tasks.Task" />.The task object representing the asynchronous operation.</returns>
+        /// <returns>
+        /// Returns <see cref="Task{TResult}" />. The task object representing the asynchronous operation
+        /// that at completion returns the transaction sync_token.
+        /// </returns>
         /// <exception cref="AggregateException">Command execution exception.</exception>
         /// <exception cref="HttpRequestException">API exception.</exception>
-        Task CommitAsync();
+        Task<string> CommitAsync();
     }
 }

src/Todoist.Net/Services/Transaction.cs

@@ -1,4 +1,4 @@
-using System;
+using System;
 using System.Collections.Generic;
 using System.Linq;
 using System.Net.Http;
@@ -59,14 +59,17 @@ internal Transaction(IAdvancedTodoistClient todoistClient)
         /// <summary>
         /// Commits the transaction asynchronous.
         /// </summary>
-        /// <returns>Returns <see cref="T:System.Threading.Tasks.Task" />.The task object representing the asynchronous operation.</returns>
+        /// <returns>
+        /// Returns <see cref="Task{TResult}" />. The task object representing the asynchronous operation
+        /// that at completion returns the transaction sync_token.
+        /// </returns>
         /// <exception cref="AggregateException">Command execution exception.</exception>
         /// <exception cref="HttpRequestException">API exception.</exception>
-        public async Task CommitAsync()
+        public async Task<string> CommitAsync()
         {
             try
             {
-                await _todoistClient.ExecuteCommandsAsync(_commands.ToArray()).ConfigureAwait(false);
+                return await _todoistClient.ExecuteCommandsAsync(_commands.ToArray()).ConfigureAwait(false);
             }
             finally
             {

src/Todoist.Net/TodoistClient.cs

@@ -262,12 +262,15 @@ public Task<T> PostFormAsync<T>(
         /// Executes the commands asynchronous.
         /// </summary>
         /// <param name="commands">The commands.</param>
-        /// <returns>Returns <see cref="T:System.Threading.Tasks.Task" />.The task object representing the asynchronous operation.</returns>
+        /// <returns>
+        /// Returns <see cref="Task{TResult}" />. The task object representing the asynchronous operation
+        /// that at completion returns the commands execution sync_token.
+        /// </returns>
         /// <exception cref="System.ArgumentNullException">Value cannot be null - commands.</exception>
         /// <exception cref="System.AggregateException">Command execution exception.</exception>
         /// <exception cref="ArgumentException">Value cannot be an empty collection.</exception>
         /// <exception cref="HttpRequestException">API exception.</exception>
-        async Task IAdvancedTodoistClient.ExecuteCommandsAsync(params Command[] commands)
+        async Task<string> IAdvancedTodoistClient.ExecuteCommandsAsync(params Command[] commands)
         {
             if (commands == null)
             {
@@ -294,6 +297,7 @@ async Task IAdvancedTodoistClient.ExecuteCommandsAsync(params Command[] commands
             {
                 UpdateTempIds(commands, syncResponse.TempIdMappings);
             }
+            return syncResponse.SyncToken;
         }
 
         /// <summary>