HomeKit support for Rollershutter Group Item

Hello,

As part of my migration to OH3, I’ve spent a considerable amount of time reworking my items setup to adhere to the Semantic Model recommendations. I have created group items with aggregation functions to represent the Equipment in my setup and added the appropriate HomeKit metadata to the group items.

Item configuration:

Group:Switch gKitchenLights "Kitchen Lights" <lightbulb>
    (gKitchen, gLights) ["WallSwitch"] {
        homekit="Lighting"
    }

This works for almost everything despite some complaining from the HomeKit binding…

[WARN ] [ternal.accessories.BooleanItemReader] - Item gKitchenLights is a org.openhab.core.items.GroupItem instead of the expected SwitchItem, ContactItem or StringItem

The one group type that hasn’t worked is Rollershutters.

Item configuration:

Group:Rollershutter gBedroomBlinds "Bedroom Blinds" <rollershutter>
    (gBedroom, gBlinds) ["Blinds"] {
        homekit="WindowCovering"
    }

This configuration creates an entry in my HomeKit app, but when I try to control it the HomeKit binding gives this warning…

[WARN ] [ssories.AbstractHomekitAccessoryImpl] - Unsupported item type for characteristic TARGET_POSITION at accessory gBedroomBlinds. Expected class org.openhab.core.library.items.RollershutterItem, got class org.openhab.core.items.GroupItem

Would it be possible to add the ability for the HomeKit binding to control Group items with supported item types the same way it would control a regular item of that type?

Created a pull request for this feature that is ready for review.