Inconsistency in Column Class Attribute Assignments for Task Timestamps

[WensiDING]

Hello,

I've noticed an issue within the Column class where there seems to be a mix-up in the assignment of timestamps for tasks. Specifically, both the tasks:created_at and tasks:updated_at fields are being assigned to the same attribute, created_at. This leads to a lack of distinction between the creation and update timestamps for tasks associated with a column, potentially causing confusion and errors in timestamp handling.