BE: fix(rbac): address PR review comments

Author: seonho-jeong

api/src/main/java/io/kafbat/ui/config/auth/RoleBasedAccessControlProperties.java

@@ -27,10 +27,6 @@ public List<Role> getRoles() {
     return roles;
   }
 
-  public void setDefaultRole(DefaultRole defaultRole) {
-    this.defaultRole = defaultRole;
-  }
-
   @Nullable
   public DefaultRole getDefaultRole() {
     return defaultRole;

api/src/main/java/io/kafbat/ui/service/rbac/AccessControlService.java

@@ -87,7 +87,8 @@ public void init() {
         .flatMap(Set::stream)
         .collect(Collectors.toSet());
 
-    if (!(properties.getRoles().isEmpty() && properties.getDefaultRole() == null)
+    boolean hasRolesConfigured = !properties.getRoles().isEmpty() || properties.getDefaultRole() != null;
+    if (hasRolesConfigured
         && "oauth2".equalsIgnoreCase(environment.getProperty("auth.type"))
         && (clientRegistrationRepository == null || !clientRegistrationRepository.iterator().hasNext())) {
       log.error("Roles are configured but no authentication methods are present. Authentication might fail.");