fix(GODT-2829): Sync Service fixes

Fix tracking of child jobs. The build stage splits the incoming work
even further, but this was not reflected in the wait group counter. This
also fixes an issue where the cache was cleared to late.

Add more debug info for analysis.

Refactor sync state interface in order to have persistent sync rate.

internal/services/syncservice/job.go

@@ -24,6 +24,7 @@ import (
 	"sync"
 
 	"github.com/ProtonMail/gluon/async"
+	"github.com/ProtonMail/go-proton-api"
 	"github.com/sirupsen/logrus"
 )
 
@@ -54,6 +55,9 @@ type Job struct {
 
 	panicHandler  async.PanicHandler
 	downloadCache *DownloadCache
+
+	metadataFetched   int64
+	totalMessageCount int64
 }
 
 func NewJob(ctx context.Context,
@@ -178,6 +182,36 @@ func (s *childJob) userID() string {
 	return s.job.userID
 }
 
+func (s *childJob) chunkDivide(chunks [][]proton.FullMessage) []childJob {
+	numChunks := len(chunks)
+
+	if numChunks == 1 {
+		return []childJob{*s}
+	}
+
+	result := make([]childJob, numChunks)
+	for i := 0; i < numChunks-1; i++ {
+		result[i] = s.job.newChildJob(chunks[i][len(chunks[i])-1].ID, int64(len(chunks[i])))
+		collectIDs(&result[i], chunks[i])
+	}
+
+	result[numChunks-1] = *s
+	collectIDs(&result[numChunks-1], chunks[numChunks-1])
+
+	return result
+}
+
+func collectIDs(j *childJob, msgs []proton.FullMessage) {
+	j.cachedAttachmentIDs = make([]string, 0, len(msgs))
+	j.cachedMessageIDs = make([]string, 0, len(msgs))
+	for _, msg := range msgs {
+		j.cachedMessageIDs = append(j.cachedMessageIDs, msg.ID)
+		for _, attach := range msg.Attachments {
+			j.cachedAttachmentIDs = append(j.cachedAttachmentIDs, attach.ID)
+		}
+	}
+}
+
 func (s *childJob) onFinished(ctx context.Context) {
 	s.job.log.Infof("Child job finished")
 	s.job.onJobFinished(ctx, s.lastMessageID, s.messageCount)