ui-even on open/close dialog

### Description

It would be good to get some info if a user opens or closes a dialog ui-group. I would relate it to the ui-event node.

### Have you provided an initial effort estimate for this issue?

I am no FlowFuse team member

Start by tracing the ui-group dialog behavior and the ui-event node mentioned in the issue. Determine how open and close actions should be represented and where the event contract is defined; the work is done when both actions provide usable information through ui-event and the relevant behavior is covered.

Written by the indexing model from the issue text.