Make TokenProvider customizable

[salbracco24]

Checklist

• I have looked into the Readme and Examples, and have not found a suitable solution or answer.
• I have looked into the API documentation and have not found a suitable solution or answer.
• I have searched the issues and have not found a suitable solution or answer.
• I have searched the Auth0 Community forums and have not found a suitable solution or answer.
• I agree to the terms within the Auth0 Code of Conduct.

Describe the problem you'd like to have solved

I want to provide custom logic to retrieve the token used to access the Auth0 Management API. Yes, I can do this by calling "setApiToken()" but that's cumbersome. I would like to implement my own token provider by implementing TokenProvider, a public interface.

Describe the ideal solution

Add a method to the builder or add a constructor for the ManagementApi class (in the com.auth0.client.mgmt package), so that TokenProvider can be changed.

You can even just make the constructor on line 35 public, but I'd prefer a new constructor, as I don't need to specify the HTTP client.

You can literally fix this issue in 10 minutes or less.

Alternatives and current workarounds

No workarounds, except reflection, which is a hack.

Additional context

Please fix this quickly, thanks.