Custom DSL Support for Webflux Security

Expected Behavior

The Servlet HttpSecurity builder supports defining a custom DSL that can be applied with the
with method.

Example:

@Configuration
@EnableWebSecurity
public class Config {
	@Bean
	public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
		http
			.with(MyCustomDsl.customDsl(), (dsl) -> dsl
				.flag(true)
			)
			// ...
		return http.build();
	}
}

It would be nice if the same could be achieved with Webflux Security and ServerHttpSecurity.

Current Behavior

Currently ServerHttpSecurity does not provide this functionality.

Start by comparing the documented Servlet custom DSL using HttpSecurity with the existing ServerHttpSecurity API. Done means WebFlux Security supports an equivalent custom DSL configuration; the issue does not name files or tests, so those entry points must be located first.