Other: Do not fail on label events

Do not treat unknown label creation/deletion/update or deletion in Bridge
as an error as the Gluon cache still needs to receive these events to
correct its internal state.

Author: LBeernaertProton

internal/user/events.go

@@ -301,11 +301,9 @@ func (user *User) handleCreateLabelEvent(_ context.Context, event proton.LabelEv
 		}).Info("Handling label created event")
 
 		if _, ok := user.apiLabels[event.Label.ID]; ok {
-			return fmt.Errorf("label %q already exists", event.ID)
+			user.apiLabels[event.Label.ID] = event.Label
 		}
 
-		user.apiLabels[event.Label.ID] = event.Label
-
 		for _, updateCh := range user.updateCh {
 			updateCh.Enqueue(newMailboxCreatedUpdate(imap.MailboxID(event.ID), getMailboxName(event.Label)))
 		}
@@ -328,11 +326,9 @@ func (user *User) handleUpdateLabelEvent(_ context.Context, event proton.LabelEv
 		}).Info("Handling label updated event")
 
 		if _, ok := user.apiLabels[event.Label.ID]; !ok {
-			return fmt.Errorf("label %q does not exist", event.ID)
+			user.apiLabels[event.Label.ID] = event.Label
 		}
 
-		user.apiLabels[event.Label.ID] = event.Label
-
 		for _, updateCh := range user.updateCh {
 			updateCh.Enqueue(imap.NewMailboxUpdated(
 				imap.MailboxID(event.ID),
@@ -356,11 +352,9 @@ func (user *User) handleDeleteLabelEvent(_ context.Context, event proton.LabelEv
 
 		label, ok := user.apiLabels[event.ID]
 		if !ok {
-			return fmt.Errorf("label %q does not exist", event.ID)
+			delete(user.apiLabels, event.ID)
 		}
 
-		delete(user.apiLabels, event.ID)
-
 		for _, updateCh := range user.updateCh {
 			updateCh.Enqueue(imap.NewMailboxDeleted(imap.MailboxID(event.ID)))
 		}