Datagrid problems with keyboard

the datagrid MaterialDataGridComboBoxColumn can't be used with keyboard

when i get to the column with my keyboard by pressing "Tab" pressing any key to open the "drop down list" including space doesn't do anything and i have to use the mouse to do so even if i forced the editing cell mode for it

can't set the MaterialDataGridComboBoxColumn to editable

pressing tab to go throw app fields work fine until i reach a datagrid instead of going from the last field to the first cell in the first row if there is any it will go throw the columns headers first then the first row.
if you need this for a checkbox to select all or something just add IsTabStop with false as the default also there is no visible indication where it currently focus on with the headers because the dots box doesn't show on them

the MaterialDesignDataGridTextColumnPopupEditingStyle should popup with minwidth as wide as the cell width.

demo https://youtu.be/d21YR-9FKk4

you can test all of this in the demo app, thanks

Beginne mit der in der Issue beschriebenen Demo-App und reproduziere das Tastaturverhalten in MaterialDataGridComboBoxColumn. Untersuche das Verhalten der Datagrid-Spalte, die Tab-Reihenfolge und die Fokusanzeige sowie MaterialDesignDataGridTextColumnPopupEditingStyle. Die Aufgabe ist erledigt, wenn die Bearbeitung per Tastatur funktioniert, die Tab-Navigation und der Fokus nutzbar sind und die minimale Breite des Popups der Zellbreite entspricht.