feat: add GetMessageID api (streamnative/pulsar-admin-go#28)

add GetMessageID api

Co-authored-by: 辛传涛 <xinchuantao@bilibili.com>
Co-authored-by: Fushu Wang <fswang@streamnative.io>

pulsaradmin/pkg/admin/topic.go

@@ -66,6 +66,9 @@ type Topics interface {
 	// GetLastMessageID returns the last commit message Id of a topic
 	GetLastMessageID(utils.TopicName) (utils.MessageID, error)
 
+	// GetMessageID returns the message Id by timestamp(ms) of a topic
+	GetMessageID(utils.TopicName, int64) (utils.MessageID, error)
+
 	// GetStats returns the stats for the topic
 	// All the rates are computed over a 1 minute window and are relative the last completed 1 minute period
 	GetStats(utils.TopicName) (utils.TopicStats, error)
@@ -377,6 +380,13 @@ func (t *topics) GetLastMessageID(topic utils.TopicName) (utils.MessageID, error
 	return messageID, err
 }
 
+func (t *topics) GetMessageID(topic utils.TopicName, timestamp int64) (utils.MessageID, error) {
+	var messageID utils.MessageID
+	endpoint := t.pulsar.endpoint(t.basePath, topic.GetRestPath(), "messageid", strconv.FormatInt(timestamp, 10))
+	err := t.pulsar.Client.Get(endpoint, &messageID)
+	return messageID, err
+}
+
 func (t *topics) GetStats(topic utils.TopicName) (utils.TopicStats, error) {
 	var stats utils.TopicStats
 	endpoint := t.pulsar.endpoint(t.basePath, topic.GetRestPath(), "stats")