Simplify chaining of OAuth2TokenValidator with JwtValidators defaults

[jzheaux]

It's common to compose the OAuth2TokenValidator<Jwt> defaults with additional validators. Here is an example from Spring Security:

class DefaultOidcIdTokenValidatorFactory implements Function<ClientRegistration, OAuth2TokenValidator<Jwt>> {

	@Override
	public OAuth2TokenValidator<Jwt> apply(ClientRegistration clientRegistration) {
		return new DelegatingOAuth2TokenValidator<>(new JwtTimestampValidator(),
				new OidcIdTokenValidator(clientRegistration));
	}

}

This could change to:

class DefaultOidcIdTokenValidatorFactory implements Function<ClientRegistration, OAuth2TokenValidator<Jwt>> {

	@Override
	public OAuth2TokenValidator<Jwt> apply(ClientRegistration clientRegistration) {
		return JwtValidators.createDefaultWithValidators(new OidcIdTokenValidator(clientRegistration));
	}

}

This convenience makes it simpler for applications to base their validation on the already-vetted Spring Security defaults, making applications more secure.