request to fix illogical and redundant code in ResourceProtector (solution provided).

[danilovmy]

Everywhere in documentation about ResourceProtector, we can find:

from authlib.integrations.django_oauth2 import ResourceProtector, BearerTokenValidator
from django.http import JsonResponse

require_oauth = ResourceProtector()
require_oauth.register_token_validator(BearerTokenValidator(OAuth2Token))

This example with an error (OAuth2Token is not imported) exists in many sources on the internet and probably in many projects. But I don't understand why it cannot be simply organized like this:

require_oauth = ResourceProtector(token_validator=BearerTokenValidator(OAuth2Token))

I don't offer to remove .register_token_validator() method completely, but i am sure: to add posibility to register token_validator on __init__ can reduce on 50% initializing code of ResourceProtector from Authlib in every project!
For example:

class Protector(ResourceProtector):
    def __init__(self, *args, **kwargs):
        validator = kwargs.pop('validator', None)
        super().__init__(*args, **kwargs)
        validator and self.register_token_validator(validator)