Stage a new quantity for an existing order line
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
The path names an EXISTING order line, the id /api/v1/orders already publishes, not a staged change. The only writable property is the quantity, which is why this is a PATCH: a PUT would promise the whole staged change is being replaced, and neither the action nor the snapshotted price is client-writable.
ABSOLUTE, never a delta, so replaying the same body converges. Removing the line entirely is POST /order-edits/{editId}/items/{lineItemId}/remove.
Response
Success
