fix(fifo): ContentBasedDeduplication + dedup window survives delete (AWS semantics)

- ContentBasedDeduplication=true: dedupId computed from body SHA-256 when not provided
- do NOT drop dedupId on message delete: AWS keeps the 5-minute window regardless
  (previously re-send after delete delivered the message again)
- utils: GetSHA256Hash

app/gosqs/send_message_batch.go

@@ -127,7 +127,13 @@ func SendMessageBatchV1(req *http.Request) (int, interfaces.AbstractResponseBody
 		}
 		msg.MD5OfMessageBody = utils.GetMD5Hash(sendEntry.MessageBody)
 		msg.GroupID = sendEntry.MessageGroupId
-		msg.DeduplicationID = sendEntry.MessageDeduplicationId
+		// ContentBasedDeduplication: dedupId вычисляется из тела (SHA-256),
+		// если не передан явно (AWS-семантика FIFO).
+		dedupID := sendEntry.MessageDeduplicationId
+		if queue.IsFIFO && queue.ContentBasedDeduplication && dedupID == "" {
+			dedupID = utils.GetSHA256Hash(sendEntry.MessageBody)
+		}
+		msg.DeduplicationID = dedupID
 		msg.Uuid = uuid.NewString()
 		msg.SentTime = time.Now()
 
@@ -135,12 +141,12 @@ func SendMessageBatchV1(req *http.Request) (int, interfaces.AbstractResponseBody
 		if queue.IsFIFO {
 			fifoSeqNumber = queue.NextSequenceNumber(sendEntry.MessageGroupId)
 		}
-		if !queue.IsDuplicate(sendEntry.MessageDeduplicationId) {
+		if !queue.IsDuplicate(dedupID) {
 			appendedIdx = append(appendedIdx, queue.AppendMessage(msg))
 			newMsgs = append(newMsgs, msg)
-			appendedDedupIDs = append(appendedDedupIDs, sendEntry.MessageDeduplicationId)
+			appendedDedupIDs = append(appendedDedupIDs, dedupID)
 		} else {
-			log.Debugf("Duplicate deduplicationId [%s] in queue [%s]", sendEntry.MessageDeduplicationId, queueName)
+			log.Debugf("Duplicate deduplicationId [%s] in queue [%s]", dedupID, queueName)
 		}
 
 		sentEntries = append(sentEntries, models.SendMessageBatchResultEntry{