BE: Throw obvious exception in case no oauth2 providers have been defined (#4002)

kafka-ui-api/src/main/java/com/provectus/kafka/ui/config/auth/OAuthSecurityConfig.java

@@ -99,6 +99,9 @@ public class OAuthSecurityConfig extends AbstractAuthSecurityConfig {
     final OAuth2ClientProperties props = OAuthPropertiesConverter.convertProperties(properties);
     final List<ClientRegistration> registrations =
         new ArrayList<>(new OAuth2ClientPropertiesMapper(props).asClientRegistrations().values());
+    if (registrations.isEmpty()) {
+      throw new IllegalArgumentException("OAuth2 authentication is enabled but no providers specified.");
+    }
     return new InMemoryReactiveClientRegistrationRepository(registrations);
   }
 

kafka-ui-api/src/main/java/com/provectus/kafka/ui/config/auth/condition/CognitoCondition.java

@@ -1,13 +1,14 @@
 package com.provectus.kafka.ui.config.auth.condition;
 
 import com.provectus.kafka.ui.service.rbac.AbstractProviderCondition;
+import org.jetbrains.annotations.NotNull;
 import org.springframework.context.annotation.Condition;
 import org.springframework.context.annotation.ConditionContext;
 import org.springframework.core.type.AnnotatedTypeMetadata;
 
 public class CognitoCondition extends AbstractProviderCondition implements Condition {
   @Override
-  public boolean matches(final ConditionContext context, final AnnotatedTypeMetadata metadata) {
+  public boolean matches(final ConditionContext context, final @NotNull AnnotatedTypeMetadata metadata) {
     return getRegisteredProvidersTypes(context.getEnvironment()).stream().anyMatch(a -> a.equalsIgnoreCase("cognito"));
   }
-}
+}