Add method to get the latest update date of the webuntis data, Fix a merge mistake

Author: Suiram1701

API.Test/TeachingTests.cs

@@ -63,4 +63,17 @@ public void GetDepartment()
         else
             Assert.Fail();
     }
+
+    [Test]
+    public void GetLatestImportTime()
+    {
+        Client.LoginAsync(s_Server, s_LoginName, s_UserName, s_Password).Wait();
+
+        Task<DateTime> time = Client.GetLatestImportTimeAsync();
+        time.Wait();
+        if (time.Result <= DateTime.Now)
+            Assert.Pass();
+        else
+            Assert.Fail();
+    }
 }

WebUntisAPI.Client/Exceptions/WebUntisException.cs

@@ -33,7 +33,7 @@ public enum Codes
             /// <summary>
             /// Json rpc method not found
             /// </summary>
-            MethodNotFound = -32601
+            MethodNotFound = -32601,
 
             /// <summary>
             /// Access denied for the requested timetable

WebUntisAPI.Client/WebUntisClient.cs

@@ -227,6 +227,22 @@ public async Task LogoutAsync(string id = "getStudents", CancellationToken ct =
                 throw new HttpRequestException($"There was an error while the http request (Code: {response.StatusCode}).");
         }
 
+        /// <summary>
+        /// Get the latest update date of the WebUntis data
+        /// </summary>
+        /// <param name="id">Identifier for the request</param>
+        /// <param name="ct">Cancellation token</param>
+        /// <returns>The latest update date in <see cref="DateTimeKind.Utc"/></returns>
+        /// <exception cref="ObjectDisposedException">Thrown when the instance was disposed</exception>
+        /// <exception cref="UnauthorizedAccessException">Thrown when the client isn't logged in</exception>
+        /// <exception cref="HttpRequestException">Thrown when an error happend while the http request</exception>
+        /// <exception cref="WebUntisException">Thrown when the WebUntis API returned an error</exception>
+        public async Task<DateTime> GetLatestImportTimeAsync(string id = "getLatestImportTime", CancellationToken ct = default)
+        {
+            long timestamp = await MakeRequestAsync<object, long>(id, "getLatestImportTime", new object(), ct);
+            return new DateTime(1970, 01, 01, 0, 0, 0, DateTimeKind.Utc).AddTicks(timestamp * 10000);
+        }
+
         /// <summary>
         /// Make an internal basic request to the WebUntis server
         /// </summary>