feat: map Keycloak realm roles to Spring RBAC

backend/src/main/java/com/example/keycloakpattern/SecurityConfig.java

@@ -7,6 +7,7 @@ import org.springframework.context.annotation.Configuration;
 import org.springframework.security.config.Customizer;
 import org.springframework.security.config.annotation.web.builders.HttpSecurity;
 import org.springframework.security.config.http.SessionCreationPolicy;
+import org.springframework.security.oauth2.server.resource.authentication.JwtAuthenticationConverter;
 import org.springframework.security.web.SecurityFilterChain;
 import org.springframework.web.cors.CorsConfiguration;
 import org.springframework.web.cors.CorsConfigurationSource;
@@ -25,12 +26,21 @@ public class SecurityConfig {
             .authorizeHttpRequests(authorize -> authorize
                 .requestMatchers("/actuator/health", "/actuator/health/**", "/api/public")
                 .permitAll()
+                .requestMatchers("/api/admin")
+                .hasRole("admin-role")
                 .anyRequest()
                 .authenticated())
-            .oauth2ResourceServer(oauth2 -> oauth2.jwt(Customizer.withDefaults()))
+            .oauth2ResourceServer(oauth2 -> oauth2.jwt(jwt ->
+                jwt.jwtAuthenticationConverter(jwtAuthenticationConverter())))
             .build();
     }
 
+    private JwtAuthenticationConverter jwtAuthenticationConverter() {
+        JwtAuthenticationConverter converter = new JwtAuthenticationConverter();
+        converter.setJwtGrantedAuthoritiesConverter(new KeycloakRealmRoleConverter());
+        return converter;
+    }
+
     @Bean
     CorsConfigurationSource corsConfigurationSource() {
         CorsConfiguration configuration = new CorsConfiguration();