[Feature request] disable tasks dragging to other rows (allow only within current row)

[Vitalik549]

For now it's possible to

• drag tasks from any row to any row
• disable dragging

It would be nice to allow dragging only within current row (tasks would slide only horizontally, y position is not changed).

Use case: think of a calendar, where row = user having multiple tasks in the row. In that scenario I'd like to disable possibility to move task to another row (which would mean assigning task to another person) but still allow to drag and drop to change start/end date of the task.