store: extract marking behavior and add tests

Separate the marking functions from the message store and extract the
marking behavior into its own class with tests.

Signed-off-by: Koni Marti <koni.marti@gmail.com>
Acked-by: Robin Jarry <robin@jarry.cc>

commands/msg/delete.go

@@ -43,9 +43,10 @@ func (Delete) Execute(aerc *widgets.Aerc, args []string) error {
 		return err
 	}
 	sel := store.Selected()
+	marker := store.Marker()
+	marker.ClearVisualMark()
 	// caution, can be nil
 	next := findNextNonDeleted(uids, store)
-	store.ClearVisualMark()
 	store.Delete(uids, func(msg types.WorkerMessage) {
 		switch msg := msg.(type) {
 		case *types.Done:
@@ -80,11 +81,11 @@ func (Delete) Execute(aerc *widgets.Aerc, args []string) error {
 				}
 			}
 		case *types.Error:
-			store.Remark()
+			marker.Remark()
 			store.Select(sel.Uid)
 			aerc.PushError(msg.Error.Error())
 		case *types.Unsupported:
-			store.Remark()
+			marker.Remark()
 			store.Select(sel.Uid)
 			// notmuch doesn't support it, we want the user to know
 			aerc.PushError(" error, unsupported for this worker")