Plugins.txt

In your all your plugins you extend QuirkPlugin now not CSharpPlugi. 
Then you can put `[ChatCommand("auth")]` style attributes on your chat commands rather than register them

QuirkPlugin.cs

public abstract class QuirkPlugin : CSharpPlugin
{
  protected Command cmd = Interface.Oxide.GetLibrary<Command>();

  public override void HandleAddedToManager(PluginManager manager)
  {
    foreach (MethodInfo method in GetType().GetMethods(BindingFlags.NonPublic | BindingFlags.Instance))
    {
       object[] attributes = method.GetCustomAttributes(typeof(ChatCommandAttribute), true);
       if (attributes.Length > 0)
       {
           if (attributes[0] is ChatCommandAttribute attribute)
           {
               cmd.AddChatCommand(attribute.Command, this, method.Name);
           }
       }
    }
  }

}