getGroupingValue takes the original row only

[dvmoritzschoefl]

Currently, it seems that the code for getting the grouping value does this

  if (!column.columnDef.getGroupingValue) {
    return row.getValue(columnId)
  }

  if (row._groupingValuesCache) {
    row._groupingValuesCache[columnId] = column.columnDef.getGroupingValue(
      row.original,
    )
  }

which means it passes the original row only. Our problem is that we rely on accessor functions as data mapping mechanism, and this architecture prevents us from defining a custom groupingValue and an accessor function at the same time, since you need the row index (of the row, not the original) to call the accessor function.

We currently have a workaround involving a cache to make the values returned by the accessor function stable, but this seams suboptimal.

Would it be a useful addition for the table to pass the row instead of row.original or does this has some side effects i am not aware of?