REST API to make requisitions not available for processing

Summary:

Content (required):

Hello,

customer needs to send purchase requisitions, once approved, to an external system for some specific activities.

When the requisition data is sent it is necessary to have an API, called by the external system, which makes such requisition not available for processing in the buyer area (e.g. REQS_IN_POOL_FLAG != for requisition lines).

Do you have any idea, and related APIs, to get this behavior.

The external system is also supposed to update some requisition flexfields for the approved requisition, suggested APIs do not work for approved requisitions. We need a solution also for that.