Carried over contracts.

code/MessengerApi.Contracts/Model/Credentials.cs

@@ -0,0 +1,15 @@
+namespace MessengerApi.Contracts
+{
+    public class Credentials
+    {
+        public string ApiKey { get; private set; }
+
+        public string ApiUrl { get; private set; }
+
+        public Credentials(string apiKey, string apiUrl)
+        {
+            ApiKey = apiKey;
+            ApiUrl = apiUrl;
+        }
+    }
+}