Edit a queued send's copy or time before it goes out

Edits a queued send before it goes out. Send any of subject, body and scheduledAt; omitted fields keep the queued row's current values. IMPORTANT: the edit is not an in-place update - the row you addressed is marked overwritten and a NEW queued row carries the content forward, so the response returns the new id (and the old one as replacedSendId) and any further edit must address the new id. Only a send still waiting to go out can be edited: a row in scheduled or approval_required, with a send time. Anything else - sent, skipped, stopped, already overwritten, replied or failed - answers 409. Only the owner of the send's campaign may edit it. Rate limit: 30 requests/minute and 1,000/day per token owner, shared by every campaign, scheduled-send, campaign-template and knowledge-hub endpoint.

Errors:

• 404 SCHEDULED_SEND_NOT_FOUND — No queued send with this id exists, or it belongs to a campaign you do not own.
• 409 SCHEDULED_SEND_NOT_EDITABLE — The send is no longer waiting to go out (sent, skipped, stopped, already overwritten, replied or failed), or it carries no send time.
• 422 VALIDATION_FAILED — Empty body, unknown key, a subject or body over its length cap, or a scheduledAt that is not an ISO 8601 date-time; param names the field.
• 429 RATE_LIMITED — More than 30 campaign requests in a minute, or 1,000 in a day, for this token owner (the bucket is shared by every /business/campaigns, /business/scheduled-sends, /business/campaign-templates and /business/knowledge-hubs call).
• 500 UNEXPECTED_ERROR — An unhandled failure; the detail stays in our logs and is never returned.

Requires one of the following token scopes: campaigns.