refactor(spring-security): refactor spring security and spring from 5.x to 6.x with spring boot upgrade to 3.x

With spring boot upgrade, spring security also upgrades from 5.x to 6.x. As per the migration [steps](https://www.baeldung.com/spring-security-migrate-5-to-6), `WebSecurityConfigurerAdapter` has been removed. So, it is not required to be extended, instead bean can be registered.

`WebMvcConfigurerAdapter` class has been deprecated in Spring 5.0 and subsequently removed from spring 6.0. So, replacing it with `WebMvcConfigurer` interface for direct implementation.
https://docs.spring.io/spring-framework/docs/5.0.0.RELEASE/javadoc-api/org/springframework/web/servlet/config/annotation/WebMvcConfigurerAdapter.html

Author: j-sandy

fiat-api/src/main/java/com/netflix/spinnaker/fiat/shared/FiatAuthenticationConfig.java

@@ -36,7 +36,7 @@
 import org.springframework.security.config.annotation.method.configuration.EnableGlobalMethodSecurity;
 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.configuration.WebSecurityConfigurerAdapter;
+import org.springframework.security.web.SecurityFilterChain;
 import org.springframework.security.web.authentication.AnonymousAuthenticationFilter;
 import org.springframework.security.web.authentication.AuthenticationConverter;
 import retrofit2.Retrofit;
@@ -92,10 +92,24 @@ AuthenticationConverter defaultAuthenticationConverter() {
     return new AuthenticatedRequestAuthenticationConverter();
   }
 
+  // Removing bean of WebSecurityConfigurerAdapter, as in spring security 6.0 it is no more
+  // required.
+  // https://github.com/spring-projects/spring-security/pull/11923
+  // https://www.baeldung.com/spring-security-migrate-5-to-6#2-websecurityconfigureradapter
   @Bean
-  FiatWebSecurityConfigurerAdapter fiatSecurityConfig(
-      FiatStatus fiatStatus, AuthenticationConverter authenticationConverter) {
-    return new FiatWebSecurityConfigurerAdapter(fiatStatus, authenticationConverter);
+  public SecurityFilterChain configure(
+      HttpSecurity http, FiatStatus fiatStatus, AuthenticationConverter authenticationConverter)
+      throws Exception {
+    return http.servletApi()
+        .and()
+        .exceptionHandling()
+        .and()
+        .anonymous()
+        .and()
+        .addFilterBefore(
+            new FiatAuthenticationFilter(fiatStatus, authenticationConverter),
+            AnonymousAuthenticationFilter.class)
+        .build();
   }
 
   @Bean
@@ -104,29 +118,4 @@ FiatAccessDeniedExceptionHandler fiatAccessDeniedExceptionHandler(
       ExceptionMessageDecorator exceptionMessageDecorator) {
     return new FiatAccessDeniedExceptionHandler(exceptionMessageDecorator);
   }
-
-  private static class FiatWebSecurityConfigurerAdapter extends WebSecurityConfigurerAdapter {
-    private final FiatStatus fiatStatus;
-    private final AuthenticationConverter authenticationConverter;
-
-    private FiatWebSecurityConfigurerAdapter(
-        FiatStatus fiatStatus, AuthenticationConverter authenticationConverter) {
-      super(true);
-      this.fiatStatus = fiatStatus;
-      this.authenticationConverter = authenticationConverter;
-    }
-
-    @Override
-    protected void configure(HttpSecurity http) throws Exception {
-      http.servletApi()
-          .and()
-          .exceptionHandling()
-          .and()
-          .anonymous()
-          .and()
-          .addFilterBefore(
-              new FiatAuthenticationFilter(fiatStatus, authenticationConverter),
-              AnonymousAuthenticationFilter.class);
-    }
-  }
 }

fiat-web/src/main/java/com/netflix/spinnaker/fiat/config/FiatConfig.java

@@ -40,12 +40,12 @@
 import org.springframework.scheduling.concurrent.ThreadPoolTaskScheduler;
 import org.springframework.web.servlet.config.annotation.ContentNegotiationConfigurer;
 import org.springframework.web.servlet.config.annotation.InterceptorRegistry;
-import org.springframework.web.servlet.config.annotation.WebMvcConfigurerAdapter;
+import org.springframework.web.servlet.config.annotation.WebMvcConfigurer;
 
 @Configuration
 @Import({RetrofitConfig.class, PluginsAutoConfiguration.class})
 @EnableConfigurationProperties(FiatServerConfigurationProperties.class)
-public class FiatConfig extends WebMvcConfigurerAdapter {
+public class FiatConfig implements WebMvcConfigurer {
 
   @Autowired private Registry registry;
 
@@ -60,7 +60,6 @@ public void addInterceptors(InterceptorRegistry registry) {
 
   @Override
   public void configureContentNegotiation(ContentNegotiationConfigurer configurer) {
-    super.configureContentNegotiation(configurer);
     configurer.favorPathExtension(false).defaultContentType(MediaType.APPLICATION_JSON);
   }