Initial commit carried over from private repo. This is V2.

code/MessengerApi.Configuration/Sources/IConfigurationSource.cs

@@ -0,0 +1,9 @@
+namespace MessengerApi.Configuration.Sources
+{
+    public interface IConfigurationSource
+    {
+        bool HasKey(string key);
+
+        T GetValue<T>(string key);
+    }
+}