Add support customizing the serverLogoutSuccessHandler for OidcClientInitiatedServerLogoutSuccessHandler

[franticticktick]

Closes gh-14778

[jzheaux]

Thanks, @CrazyParanoid! I've left my feedback inline.

[jzheaux]

Please have these be final and in the constructor

[franticticktick]

I can add final to the class, but I'm not sure if it's worth making all the fields final and initializing them in the constructor. The DefaultRedirectUriResolver requires two attributes Authentication and ServerWebExchange and this attributes are passed to the onLogoutSuccess method, meaning they cannot be null, so they can be made final and added to the constructor, ClientRegistration will be found in the resolver (OidcClientInitiatedServerLogoutSuccessHandler. this.clientRegistrationRepository::findByRegistrationId). That is, it cannot be declared final and required to be initialized in the constructor. I can easily pass it via setter if I need another one ClientRegistration:

this.handler.setRedirectUriResolver((params) -> {
			params.setClientRegistration(ClientRegistration.withRegistrationId("clientId")
					.build());
			return Mono.just("URL");});