fix: error message when changing credentials

Received error message: TwitchLib.Client.Exceptions.IllegalAssignmentException: While the client is connected, you are unable to change the connection credentials. Please disconnect first and then change them.

Updating the code to only run the credential changes when there is an
actual change. Disconnecting before we change the credentials.

Author: ProgrammingByPermutation

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

@@ -108,10 +108,15 @@ public static TwitchClientProxy Instance {
   public string? TwitchOAuthToken {
     get => _twitchOAuthToken;
     set {
+      if (value == _twitchOAuthToken) {
+        return;
+      }
+      
       _twitchOAuthToken = value;
 
       // If we have a client, try to connect.
       if (null != _client) {
+        _client.Disconnect();
         _client.SetConnectionCredentials(new ConnectionCredentials(TwitchUsername, value));
         Connect();
       }