chore(mailserver)_: reduce debug logs size in messenger_mailserver

Logs from `messenger_mailserver` occupy 40 out of 100MB of data in
my `geth.log`.

Instead of extending `logger` with many parameters, such as `chatIDs`,
`topic`, etc., the hash of those parameters is calucalted and kept as a
context.

iterates: #5889

protocol/messenger_mailserver.go

@@ -2,6 +2,8 @@ package protocol
 
 import (
 	"context"
+	"crypto/sha256"
+	"encoding/hex"
 	"fmt"
 	"math"
 	"sort"
@@ -756,15 +758,15 @@ func processMailserverBatch(
 	for _, t := range batch.Topics {
 		topicStrings = append(topicStrings, t.String())
 	}
-	logger = logger.With(zap.Any("chatIDs", batch.ChatIDs),
+	logger = logger.With(zap.String("batch hash", batch.Hash()))
+	logger.Info("syncing topic",
+		zap.Any("chatIDs", batch.ChatIDs),
 		zap.String("fromString", time.Unix(int64(batch.From), 0).Format(time.RFC3339)),
 		zap.String("toString", time.Unix(int64(batch.To), 0).Format(time.RFC3339)),
 		zap.Any("topic", topicStrings),
 		zap.Int64("from", int64(batch.From)),
 		zap.Int64("to", int64(batch.To)))
 
-	logger.Info("syncing topic")
-
 	wg := sync.WaitGroup{}
 	workWg := sync.WaitGroup{}
 	workCh := make(chan work, 1000)       // each batch item is split in 10 topics bunch and sent to this channel
@@ -959,6 +961,12 @@ type MailserverBatch struct {
 	ChatIDs     []string
 }
 
+func (mb *MailserverBatch) Hash() string {
+	data := fmt.Sprintf("%d%d%s%s%v%v", mb.From, mb.To, mb.Cursor, mb.PubsubTopic, mb.Topics, mb.ChatIDs)
+	hash := sha256.Sum256([]byte(data))
+	return hex.EncodeToString(hash[:4])
+}
+
 func (m *Messenger) SyncChatFromSyncedFrom(chatID string) (uint32, error) {
 	chat, ok := m.allChats.Load(chatID)
 	if !ok {