Releases the whole inventory hold, so the held units can be shipped again.

General description

• Unlike creating and updating a hold, releasing works in any receiving status, also once receiving has started.
• A hold that is still awaiting_review (created in the ShipMonk app and not yet approved by ShipMonk) ends cancelled instead of released; the response message tells which of the two happened.
• The call is idempotent, so releasing an already released hold succeeds and changes nothing.