Context:
On the backend we need to do a date histogram aggregation when grouping by variables of type date. The backend task for this is OPT-2533.
To decide when to do which aggregation we need the variable type in the request, as determining that without it would be a bit complicated on the backend.

AT:

• the frontend sends the variable type in the groupBy

for example:

groupBy: {
  type: 'inputVariable',
  value: {
    id: 'anInputVariableId',
    name: 'anInputVariableName',
    type: 'Date'
  }
}