Allow for configuring an Authentication Converter for OAuth Resource Server opaque tokens

[bdemers]

Summary

The new opaque token support is great!

I'd love it if the API matched the JWT equivalent with regards to configuration an authentication converter. For example:

httpSecurity.oauth2ResourceServer().jwt().jwtAuthenticationConverter(...)

Maybe something like:

httpSecurity.oauth2ResourceServer().opaqueToken().tokenAuthenticationConverter(...)

Where the converter would take a Map<String, Object> of claims.

Basically just allowing the additional processing to convert custom claims into authorities, similar to what how OAuth2IntrospectionAuthenticationProvider works:

spring-security/oauth2/oauth2-resource-server/src/main/java/org/springframework/security/oauth2/server/resource/authentication/OAuth2IntrospectionAuthenticationProvider.java

Lines 129 to 135 in b1195e7

	private Collection<GrantedAuthority> extractAuthorities(Map<String, Object> claims) {
	Collection<String> scopes = (Collection<String>) claims.get(SCOPE);
	return Optional.ofNullable(scopes).orElse(Collections.emptyList())
	.stream()
	.map(authority -> new SimpleGrantedAuthority("SCOPE_" + authority))
	.collect(Collectors.toList());
	}

Since this is possible already for JWT tokens adding something similar for opaque tokens would be great.

Thanks!

[rwinch]

Thanks for the report @bdemers! @jzheaux will look at this soon

[jzheaux]

@bdemers, thanks for the report! Glad to hear you like the support.

This feature definitely appears useful, and we're looking into addressing it in #6830.

[jzheaux]

Closing in favor of #6830