Cancel Bulk Sync Schema
Requests cancellation of any running executions for a specific schema on a bulk sync.
Cancellation is asynchronous. A successful response means the cancellation
signal for this schema has been queued; the schema's in-flight work continues
until the signal is processed. Poll
`GET /api/bulk/syncs/{id}/schemas/{schema_id}` and the parent execution via
`GET /api/bulk/syncs/{id}/status` to confirm the schema has reached a terminal
state.
