[HxMultiSelectGridColumnInternal] Support multi-select display in last column

[Arnnes]

In some cases I need to display a column with checkboxes as the last column instead of the first. I will create a pull request to add this feature.

[hakenr]

@Arnnes How will the API look like?

[Arnnes]

@hakenr For HxMultiSelectGridColumnInternal, I would like to add a parameter (probably a boolean) to indicate whether it should be the last column. Then, the GetColumnOrder method would look like this: protected override int GetColumnOrder() => IsLastGridColumn ? int.MaxValue : int.MinValue;. I'm not yet sure how to integrate this into HxGrid.

[hakenr]

Ad-hoc brainstorming:

• <HxGrid MultiSelectColumnOrder="99" />
• <HxGrid MultiSelectColumnPlacement="GridMultiSelectColumnPlacement.Start|End" />
• allow placing <HxMultiSelectGridColumn /> wherever you need to <Columns> section (when not found and multi-selection is enabled, the column is automatically added as first column)

@crdo @jirikanda Opinions / ideas?

[crdo]

+1 for <HxGrid MultiSelectColumnPlacement="GridMultiSelectColumnPlacement.Start|End" />

[jirikanda]

+1 for allow placing <HxMultiSelectGridColumn /> wherever you need

[Arnnes]

<HxGrid MultiSelectColumnPlacement="GridMultiSelectColumnPlacement.Start|End" /> is sufficient for my case (at least for now). However, I am not against to allowing to be placed wherever you need, though. @hakenr your thoughts?

[hakenr]

TBH, I'm not a big fan of adding numerous tiny parameters to configure subtle component behavior. It clutters the API and makes future improvements and adjustments harder (especially with breaking changes).

So, I prefer allowing explicit column usage while automatically adding it when not found:

• Allow placing <HxMultiSelectGridColumn /> anywhere in the <Columns> section. If not found and multi-selection is enabled, the column is automatically added as the first column.