Allow loading an existing session into an IAuth (create a UserSession, pass it in)

IF.Lastfm.Core/Api/Auth.cs

@@ -30,6 +30,17 @@ public Auth(string apikey, string secret)
             _apiSecret = secret;
         }
 
+        /// <summary>
+        /// Load an existing user session
+        /// </summary>
+        /// <param name="session">Session to load</param>
+        /// <returns>Whether session object is valid</returns>
+        public bool LoadSession(UserSession session)
+        {
+            User = session;
+            return true;
+        }
+
         public async Task<LastResponse> GetSessionTokenAsync(string username, string password)
         {
             const string apiMethod = "auth.getMobileSession";

IF.Lastfm.Core/Api/IAuth.cs

@@ -11,6 +11,13 @@ public interface IAuth
         string ApiKey { get; }
         UserSession User { get; }
 
+        /// <summary>
+        /// Load an existing user session object.
+        /// </summary>
+        /// <param name="session"></param>
+        /// <returns>Whether session object is valid</returns>
+        bool LoadSession(UserSession session);
+
         /// <summary>
         /// Gets the session token which is used as authentication for any service calls.
         /// Username and password aren't stored.