backend: add leader epoch to partition api response

backend/pkg/console/topic_partitions.go

@@ -82,6 +82,12 @@ type TopicPartitionMarks struct {
 
 	// High water mark for this partition
 	High int64 `json:"waterMarkHigh"`
+
+	// LeaderEpoch, proposed in KIP-320 and introduced in Kafka 2.1.0 is the
+	// epoch of the broker leader.
+	//
+	// This field has a default of -1.
+	LeaderEpoch int32 `json:"leaderEpoch"`
 }
 
 // TopicPartitionLogDirs contains the reported log dir size for a single partition as reported by one
@@ -184,6 +190,7 @@ func (s *Service) GetTopicDetails(ctx context.Context, topicNames []string) ([]T
 					WaterMarksError: errToString(partitionMarks.Error),
 					Low:             partitionMarks.Low,
 					High:            partitionMarks.High,
+					LeaderEpoch:     partition.LeaderEpoch,
 				},
 				PartitionLogDirs: logDirs,
 			}