Updates the CollectionOrder resource.

This endpoint allows you to update an existing collection order. All fields are optional — only fields present in the request body are updated. The following fields cannot be modified: debtor_number, payment_reference, total_amount (recalculated from invoices), started_at, and client. ### Status transitions The status field supports the following transitions: - cancel — only if current status is not paid, cancel, or merged - withdraw — only if current status is not paid, withdraw, or merged - paid — only if current status is not paid - pause — only if current status is active - active — only if current status is pause or payment_scheduled - payment_scheduled — only if current status is active When the status changes, status_datetime is automatically updated. #### Side effects of withdraw Setting the status to withdraw cascades to the order's communications: - All associated messages are automatically withdrawn. - All documents hosted for the debtor on the self-service page are set to not visible; the debtor can no longer open them through the portal. This is permanent: a withdraw cannot be undone, so the documents stay hidden once the order is withdrawn. Only the self-service page is affected. A document already delivered physically (for example a paper attachment sent by post) stays with the debtor and cannot be recalled. ### Flow switch To switch to a different flow, provide both flow_id and flow_step together. Providing only one will result in a validation error. Optionally provide flow_datetime to schedule the new flow. ### Variables The variables field uses merge semantics — only the provided variables are updated, existing variables are preserved. For example, sending {"variable3": "new value"} only updates variable 3. ### Invoices When invoices is provided, the entire invoice set is replaced. All existing invoices are removed and replaced with the new ones. The total_amount is automatically recalculated.