update procurement contract attachment using rest API for Bulk contracts

Summary:

hi Team,

We have a customer ask for procurement contracts where meta data is migrated but its not reflecting in contracts page. so we are looking for option to updated the attachments section of contracts to update with the attachment detail. since the contracts volume is huge we are trying to explore the option of rest API to update the contracts. Appreciate your help on the approach. we are looking for a sample pay load or if its possible to update the existing contracts ( high volume of contracts) with the attachment detail. I had verified the below page it