Changes to Update a task. A full replacement: omitted fields are cleared. `complete` true completes the task and stamps `completedUtc` and `completedBy`; false re-opens it and clears both. `sequence` is the public reorder — a value of 1 or more moves the task to that step, alongside any task already there; omitted or below 1 leaves it where it is. `relatedRecord` is ignored: a task stays on the record it was created on.

PUT /api/tasks/{id}