Specify sort order in column def

[kfalicov]

I'd like to be able to specify a sort order, so that I can have a column that is only sortable by asc or false (unsorted)
A potential interface for this (in the column def) might be

sortOrder: ["asc"]

or potentially

getNextSortOrder: (currentSortOrder: SortDirection | false) => SortDirection | false

in the first suggestion, an array is provided with the SortDirections. Toggling the sort of a column via column.toggleSorting invokes column.getNextSortingOrder(), which would internally reference the provided columndef sortOrder, and select the next item in the array. When the end of the array is reached, the next toggle would set the sort to false unless the enableSortingRemoval is false, in which case it would loop back around to the beginning of the array.

In the second suggestion, the column can be defined with an optional function that takes the current column.getIsSorted() value as a param, and returns the next sorting state. Nothing fancy, but it would allow for the column def to directly affect the toggled sort value. I could define my function as

getNextSortOrder: (current) => (current ? false : "asc"),

which would effectively prevent the column from ever being sorted as "desc"

Other ways would also be great, such as booleans for enableSortingDesc or enableSortingAsc (to follow the semantics of enableSortingRemoval).