When an injection is being created, we also pass postprocessing for all channels:
{
  "D": [{}, {}, {}, {}, {}, {}], // 6 postprocessings
  "D1": [],
  "AD": []
}
Then, on the backend side, we link postprocessings with measurements.
Then, the scheduler finds uncompleted postprocessings for finished injections and runs them.
We need to add a status field for postprocessing to implement the above.