Added missing Endpoint Message

Billbee.Api.Client/Endpoint/Interfaces/IOrderEndPoint.cs

@@ -194,5 +194,14 @@ ApiResult<List<InvoiceDetail>> GetInvoiceList(
         /// <param name="parsePlaceholdersQuery">The text to be parsed</param>
         /// <returns>The parsed text</returns>
         ParsePlaceholdersResult ParsePlaceholders(long orderId, ParsePlaceholdersQuery parsePlaceholdersQuery);
+
+
+        /// <summary>
+        /// Adds a message to the specified order
+        /// </summary>
+        /// <param name="orderId">The id of the order to add the message</param>
+        /// <param name="orderMessage">The content of the Order-Message</param>
+        void AddMessage(long orderId, OrderMessage orderMessage);
+
     }
 }

Billbee.Api.Client/Endpoint/OrderEndPoint.cs

@@ -287,5 +287,13 @@ public ParsePlaceholdersResult ParsePlaceholders(long orderId, ParsePlaceholders
         {
             return _restClient.Post<ParsePlaceholdersResult>($"/orders/{orderId}/parse-placeholders", parsePlaceholdersQuery);
         }
+
+
+        [ApiMapping("/api/v1/orders/{id}/message", HttpOperation.Post)]
+        public void AddMessage(long orderId, OrderMessage orderMessage)
+        {
+            _restClient.Post($"/orders/{orderId}/message", orderMessage);
+        }
+
     }
 }

Billbee.Api.Client/Model/OrderMessage.cs

@@ -0,0 +1,24 @@
+using System;
+using System.Collections.Generic;
+using System.Text;
+
+namespace Billbee.Api.Client.Model
+{
+    public class OrderMessage
+    {
+        /// <summary>
+        /// Sets the message as internal if true
+        /// </summary>
+        public bool IsInternal { get; set; }
+
+        /// <summary>
+        /// The name of the sender
+        /// </summary>
+        public string SenderName { get; set; }
+
+        /// <summary>
+        /// The text of the message
+        /// </summary>
+        public string Text { get; set; }
+    }
+}