Added list of failure reasons.

Author: sauroter

src/main/java/com/hivemq/extensions/kafka/api/services/KafkaTopicService.java

@@ -102,6 +102,14 @@ enum KafkaTopicState {
         /**
          * FAILURE signals that the operation for the topic was not successful. No possible information about the true
          * state of this topic on the Kafka cluster can be assumed.
+         * <p>
+         * Reasons for FAILURE can include, but are not limited to:
+         * <p><ul>
+         * <li> Network degradation between HiveMQ and the Kafka cluster
+         * <li> Insufficient permissions to perform the operation
+         * <li> An unsuitable configuration in either the HiveMQ Enterprise Extension for Kafka or the Kafka cluster
+         * <li> The internal state of the Kafka cluster
+         * </ul><p>
          *
          * @since 4.4.0
          */