Take a discount out of a campaign budget
Authorizations
A secret API key. Publishable keys cannot reach this API. A key may carry an expiry, and an expired key is refused exactly like an unknown one, with a 401 that names no reason; check the key's expires_at in the dashboard rather than inferring it from a response. When a merchant rolls a key's secret they choose a grace window of up to 3 days, and for its duration BOTH the new secret and the one it replaced authenticate, so an integration moves over on its own deploy schedule instead of at the instant the button is pressed. Move before the window closes: after it, the old secret is refused. Nothing else about this contract moves with a roll. The key keeps its id and its scopes, so the only thing an integration updates is the credential itself.
Headers
A unique key per logical write. Replaying a request with the same key returns the first response byte for byte instead of applying the write twice.
Body
Takes no parameters, and an empty body is expected. The discount keeps working and simply stops drawing on this budget; attaching again restores the link exactly, which is why this is a POST and not a DELETE. A discount that is not in THIS campaign is 409 promotion_not_in_campaign rather than a silent success, because it may well be in a different one and a 200 would tell a caller who typed the wrong campaign id that a link has been removed while the real one keeps drawing on the real budget. The response is the membership reference with campaign_id null, which is the proof the link is gone.
Response
Success
