Consider adding PrincipalResolver to ExchangeFilterFunctions #16284
Description
We should align (Server|Servlet)OAuth2AuthorizedClientExchangeFilterFunction with OAuth2ClientHttpRequestInterceptor which introduces a PrincipalResolver as a flexible strategy for resolving the Authentication for a given request.
For ServletOAuth2AuthorizedClientExchangeFilterFunction, the interface could be:
@FunctionalInterface
public interface PrincipalResolver {
@Nullable
Authentication resolve(ClientRequest request);
}
For ServerOAuth2AuthorizedClientExchangeFilterFunction, it may need to return a Mono<Authentication> to accommodate ReactiveSecurityContextHolder:
@FunctionalInterface
public interface PrincipalResolver {
@Nullable
Mono<Authentication> resolve(ClientRequest request);
}