Combines two or more scheduled payments on an order into one new scheduled payment. Use it to collect several open payments in a single charge.

A scheduled payment is a planned future collection on an instalment, subscription or metered order. It shows as one billing event in the order's payment timeline.

• You can merge payments that are scheduled, failed (soft declined) or rejected (hard declined). IDs that don't belong to this order are ignored.
• The new payment's amount is the sum of the originals. You can't set it.
• The originals get status merged and are never collected.
• Set the new payment's date with process_date. With now, it's charged straight away.
• The response has the new payment in scheduled_payment, and the order's full schedule in scheduled_payments.

You can't undo a merge. To change the new payment, reschedule or skip it.