[BAEL-11597] Move and update Etags article

* Moved etags article related code
* Fixed existing etag Ignored test
* Added etag scentsio adding etag support to a single endpoint
* Added tests for single endpoint etag scenario
* Cleaned now unused code in spring-rest-full module

spring-rest-full/src/main/java/org/baeldung/spring/Application.java

@@ -8,11 +8,9 @@ import org.springframework.boot.autoconfigure.EnableAutoConfiguration;
 import org.springframework.boot.autoconfigure.SpringBootApplication;
 import org.springframework.boot.builder.SpringApplicationBuilder;
 import org.springframework.boot.web.support.SpringBootServletInitializer;
-import org.springframework.context.annotation.Bean;
 import org.springframework.context.annotation.ComponentScan;
 import org.springframework.scheduling.annotation.EnableScheduling;
 import org.springframework.web.context.request.RequestContextListener;
-import org.springframework.web.filter.ShallowEtagHeaderFilter;
 
 /**
  * Main Application Class - uses Spring Boot. Just run this as a normal Java
@@ -40,8 +38,4 @@ public class Application extends SpringBootServletInitializer {
         SpringApplication.run(Application.class, args);
     }
 
-    @Bean
-    public ShallowEtagHeaderFilter shallowEtagHeaderFilter() {
-        return new ShallowEtagHeaderFilter();
-    }
 }