Add delegating filter proxy Kotlin samples to docs

Issue gh-8172

docs/manual/src/docs/asciidoc/_includes/servlet/architecture/delegating-filter-proxy.adoc

@@ -16,7 +16,8 @@ The pseudo code of `DelegatingFilterProxy` can be seen below.
 
 .`DelegatingFilterProxy` Pseudo Code
 ====
-[source,java,subs="+quotes,+macros"]
+.Java
+[source,java,role="primary",subs="+quotes,+macros"]
 ----
 public void doFilter(ServletRequest request, ServletResponse response, FilterChain chain) {
 	// Lazily get Filter that was registered as a Spring Bean
@@ -26,6 +27,18 @@ public void doFilter(ServletRequest request, ServletResponse response, FilterCha
 	delegate.doFilter(request, response);
 }
 ----
+
+.Kotlin
+[source,kotlin,role="secondary",subs="+quotes,+macros"]
+----
+fun doFilter(request: ServletRequest, response: ServletResponse, chain: FilterChain) {
+	// Lazily get Filter that was registered as a Spring Bean
+	// For the example in <<servlet-delegatingfilterproxy-figure>> `delegate` is an instance of __Bean Filter~0~__
+	val delegate: Filter = getFilterBean(someBeanName)
+	// delegate work to the Spring Bean
+	delegate.doFilter(request, response)
+}
+----
 ====
 
 Another benefit of `DelegatingFilterProxy` is that it allows delaying looking `Filter` bean instances.