Greetings

Related to this issue, when you use multiple groups, then the header of the first subgroup doesn't get rendered. This cascades down all sublevels.
Example: https://codesandbox.io/s/strange-benji-3m9d19?file=/src/app/app.component.ts 

As I was typing this up I also noticed that we don't have access to the field we're grouping on in the kendoDropDownListGroupTemplate (not exclusive to the DropDownList, all dropdown types have this problem).

It'd be great and a very minor change to enable this.
It's currently like this (line 103 inside common/list.component.ts in the source code): 

[templateContext]="{
    templateRef: groupTemplate.templateRef,
    $implicit: dataItem.value
}"

[templateContext]="{
    templateRef: groupTemplate.templateRef,
    $implicit: dataItem.value,
    field: dataItem.field
}"

Regards