Add several different public keys for one Tokenvalidator, or allow several Validators for one auth_type in ResourceProtector

[danilovmy]

We use AWS Cognito for token generation. Following this, we implement ResourceProtector in various Python sources.

To verify a token, AWS provides documentation at:
https://docs.aws.amazon.com/cognito/latest/developerguide/amazon-cognito-user-pools-using-tokens-verifying-a-jwt.html
AWS Cognito offers several public keys to decode a token. Among them, the key declared in the header should be used.

However, I can only define a TokenValidator with a single public key. ResourceProtector consumes only one TokenValidator for one auth_type. In the case of Cognito, I would need to hard override all classes because everything is hardcoded.

I ask to add possibility to work with couple of public keys for tocken.decode.

p.s. Translated with Chat GPT. If my ask is not clear - i can add information.