Obsolete warning for authenticator class. #1636

Expected Behavior

Implementing custom authenticator should not result error:
warning CS0618: 'Parameter' is obsolete: 'Use Add[XXX]Parameter methods of IRestRequest instead of instantiating the Parameter class.'

Actual Behavior

When implementing custom authenticator based on Docs and actual build in code from:
https://github.com/restsharp/RestSharp/tree/dev/src/RestSharp/Authenticators
https://restsharp.dev/usage/authenticators.html#custom-authenticator

I'm receiving an error:
warning CS0618: 'Parameter' is obsolete: 'Use Add[XXX]Parameter methods of IRestRequest instead of instantiating the Parameter class.'

The AuthenticatorBase class requires override

protected abstract Parameter GetAuthenticationParameter(string accessToken);

method

and does not allow override

public void Authenticate(IRestClient client, IRestRequest request)

method.

The build in authenticators are using forbidden statement.

To be consistent all authenticator code should be removed and and moved to AddXXXAuthentication methods.