Penultimate round of db.DefaultContext refactor (#27414)

Part of #27065

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Co-authored-by: Lunny Xiao <xiaolunwen@gmail.com>

services/auth/sync.go

@@ -15,7 +15,7 @@ import (
 func SyncExternalUsers(ctx context.Context, updateExisting bool) error {
 	log.Trace("Doing: SyncExternalUsers")
 
-	ls, err := auth.Sources()
+	ls, err := auth.Sources(ctx)
 	if err != nil {
 		log.Error("SyncExternalUsers: %v", err)
 		return err