Topics: Fix config fetch for Azure EH (#105)

Co-authored-by: Aleksei Zotov <azotcsit@gmail.com>

api/src/main/java/io/kafbat/ui/service/ReactiveAdminClient.java

@@ -77,6 +77,7 @@
 import org.apache.kafka.common.errors.InvalidRequestException;
 import org.apache.kafka.common.errors.SecurityDisabledException;
 import org.apache.kafka.common.errors.TopicAuthorizationException;
+import org.apache.kafka.common.errors.UnknownServerException;
 import org.apache.kafka.common.errors.UnknownTopicOrPartitionException;
 import org.apache.kafka.common.errors.UnsupportedVersionException;
 import org.apache.kafka.common.requests.DescribeLogDirsResponse;
@@ -246,8 +247,10 @@ public Mono<Map<String, List<ConfigEntry>>> getTopicsConfig() {
     return listTopics(true).flatMap(topics -> getTopicsConfig(topics, false));
   }
 
-  //NOTE: skips not-found topics (for which UnknownTopicOrPartitionException was thrown by AdminClient)
-  //and topics for which DESCRIBE_CONFIGS permission is not set (TopicAuthorizationException was thrown)
+  /*
+  NOTE: skips not-found topics (for which UnknownTopicOrPartitionException or UnknownServerException was thrown by
+  AdminClient) and topics for which DESCRIBE_CONFIGS permission is not set (TopicAuthorizationException was thrown)
+   */
   public Mono<Map<String, List<ConfigEntry>>> getTopicsConfig(Collection<String> topicNames, boolean includeDoc) {
     var includeDocFixed = includeDoc && getClusterFeatures().contains(SupportedFeature.CONFIG_DOCUMENTATION_RETRIEVAL);
     // we need to partition calls, because it can lead to AdminClient timeouts in case of large topics count
@@ -269,6 +272,7 @@ private Mono<Map<String, List<ConfigEntry>>> getTopicsConfigImpl(Collection<Stri
             resources,
             new DescribeConfigsOptions().includeSynonyms(true).includeDocumentation(includeDoc)).values(),
         UnknownTopicOrPartitionException.class,
+        UnknownServerException.class,
         TopicAuthorizationException.class
     ).map(config -> config.entrySet().stream()
         .collect(toMap(