fix: twitch client not receiving updated credentials

If the credentials needed to change (not be set for the first time but
actually change from one value to another), their value wasn't being
pushed to the underlying client. We now pass the credentials to the same
place as the initialization.

closes nullinside-development-group/nullinside-twitch-streaming-tools#20

Author: ProgrammingByPermutation

src/Nullinside.Api.Common/Twitch/TwitchClientProxy.cs

@@ -73,6 +73,8 @@ public class TwitchClientProxy : ITwitchClientProxy {
   /// </summary>
   private WebSocketClient? socket;
 
+  private string? _twitchOAuthToken;
+
   /// <summary>
   ///   Initializes a new instance of the <see cref="TwitchClientProxy" /> class.
   /// </summary>
@@ -103,7 +105,18 @@ public static TwitchClientProxy Instance {
   public string? TwitchUsername { get; set; }
 
   /// <inheritdoc />
-  public string? TwitchOAuthToken { get; set; }
+  public string? TwitchOAuthToken {
+    get => _twitchOAuthToken;
+    set {
+      _twitchOAuthToken = value;
+      
+      // If we have a client, try to connect.
+      if (null != client) {
+        client.SetConnectionCredentials(new ConnectionCredentials(TwitchUsername, value));
+        Connect();
+      }
+    }
+  }
 
   /// <inheritdoc />
   public void Dispose() {