Configure application base path

[AlexOreshkevich]

Make Swagger available on the custom root endpoint

@Configuration
@EnableWebFlux
public class WebConfig implements WebFluxConfigurer {

  @NotNull
  @Value("${spring.webflux.base-path}")
  private String basePath;

  @Override
  public void configurePathMatching(PathMatchConfigurer configurer) {
    configurer
        .setUseCaseSensitiveMatch(true)
        .setUseTrailingSlashMatch(false)
        .addPathPrefix(basePath,
            HandlerTypePredicate.forAnnotation(RestController.class));
  }
}

application.yml

spring:
  webflux:
    base-path: /demo