Use idiomatic Kotlin in custom filter documentation

This will make Kotlin and all users more native and readable.

Closes: gh-18967

Signed-off-by: Andrey Litvitski <andrey1010102008@gmail.com>

docs/modules/ROOT/pages/servlet/architecture.adoc

@@ -246,9 +246,15 @@ Instead of implementing `Filter`, you can extend from {spring-framework-api-url}
 Now, you need to add the filter to the <<servlet-securityfilterchain>>.
 The previous description already gives us a clue on where to add the filter, since we need to know the current user, we need to add it after the authentication filters.
 
-Based on the rule of thumb, add it after xref:servlet/authentication/anonymous.adoc[ `AnonymousAuthenticationFilter`], the last authentication filter in the chain, like so:
+Based on the rule of thumb, you can add it before xref:servlet/authentication/logout.adoc[`LogoutFilter`], like so:
 
-include-code::./SecurityConfig[tag=snippet,indent=0]
+include-code::./SecurityConfig[tag=snippet-before,indent=0]
+
+<1> Use `HttpSecurity#addFilterBefore` to add the `TenantFilter` before the `LogoutFilter`.
+
+Or after xref:servlet/authentication/anonymous.adoc[`AnonymousAuthenticationFilter`], the last authentication filter in the chain, like so:
+
+include-code::./SecurityConfig[tag=snippet-after,indent=0]
 
 <1> Use `HttpSecurity#addFilterAfter` to add the `TenantFilter` after the `AnonymousAuthenticationFilter`.
 

docs/src/test/java/org/springframework/security/docs/servlet/addingcustomfilter/SecurityConfig.java

@@ -22,6 +22,7 @@ import org.springframework.security.config.annotation.web.builders.HttpSecurity;
 import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity;
 import org.springframework.security.web.SecurityFilterChain;
 import org.springframework.security.web.authentication.AnonymousAuthenticationFilter;
+import org.springframework.security.web.authentication.logout.LogoutFilter;
 import org.springframework.test.context.ContextConfiguration;
 
 @Configuration
@@ -29,14 +30,24 @@ import org.springframework.test.context.ContextConfiguration;
 @EnableWebSecurity
 public class SecurityConfig {
 
-	// tag::snippet[]
+	// tag::snippet-before[]
 	@Bean
-	public SecurityFilterChain filterChain(HttpSecurity http) throws Exception {
+	public SecurityFilterChain filterChainBefore(HttpSecurity http) throws Exception {
+		http
+			// ...
+			.addFilterBefore(new TenantFilter(), LogoutFilter.class); // <1>
+		return http.build();
+	}
+	// end::snippet-before[]
+
+	// tag::snippet-after[]
+	@Bean
+	public SecurityFilterChain filterChainAfter(HttpSecurity http) throws Exception {
 		http
 			// ...
 			.addFilterAfter(new TenantFilter(), AnonymousAuthenticationFilter.class); // <1>
 		return http.build();
 	}
-	// end::snippet[]
+	// end::snippet-after[]
 
 }

docs/src/test/kotlin/org/springframework/security/kt/docs/servlet/addingcustomfilter/SecurityConfig.kt

@@ -20,21 +20,35 @@ import org.springframework.context.annotation.Bean
 import org.springframework.context.annotation.Configuration
 import org.springframework.security.config.annotation.web.builders.HttpSecurity
 import org.springframework.security.config.annotation.web.configuration.EnableWebSecurity
+import org.springframework.security.config.annotation.web.invoke
 import org.springframework.security.web.SecurityFilterChain
 import org.springframework.security.web.authentication.AnonymousAuthenticationFilter
+import org.springframework.security.web.authentication.logout.LogoutFilter
 
 @Configuration
 @EnableWebSecurity
 open class SecurityConfig {
 
-	// tag::snippet[]
+    // tag::snippet-before[]
     @Bean
-	open fun filterChain(http: HttpSecurity): SecurityFilterChain {
-		http
+    open fun filterChainBefore(http: HttpSecurity): SecurityFilterChain {
+        http {
             // ...
-			.addFilterAfter(TenantFilter(), AnonymousAuthenticationFilter::class.java) // <1>
+            addFilterBefore<LogoutFilter>(TenantFilter()) // <1>
+        }
         return http.build()
     }
-	// end::snippet[]
+    // end::snippet-before[]
+
+    // tag::snippet-after[]
+	@Bean
+	open fun filterChainAfter(http: HttpSecurity): SecurityFilterChain {
+		http {
+			// ...
+			addFilterAfter<AnonymousAuthenticationFilter>(TenantFilter()) // <1>
+		}
+		return http.build()
+	}
+    // end::snippet-after[]
 
 }