Chat list items can open a context on right click as well, so `StatusChatList`
needs to provide an API for users to pass down a `StatusPopupMenu` accordingly.
This is now possible with a dedicated `popupMenu` proporty that can be
used as follows:
```qml
StatusChatList {
...
popupMenu: StatusPopupMenu {
property string chatId
openHandler: function () {
...
}
StatusMenuItem {
...
}
...
}
}
```
As will all `popupMenu` properties in StatusQ component, having this explicit API
option enables us to have control over how triggering components (in this case chat
list items) behave when they open a context menu (e.g. keeping them highlighted as long
as the menu is active).
When defining a `chatId` property, `StatusChatList` will hydrate it with the id of
the chat list item that has triggered the menu.
If there's more logic to be executed upon opening the menu, `openHandler` serves
as a hook similar to other popup menus. Inside the hook, users have access to the
specific `chatId`.
Closes#171
c2f418205f