FEATURE: display warning when sharing a topic in a restricted category (PR #14820)

If a topic belongs to a category that is not readable by everyone, display a text warning of “Only visible to members of groups: [group_a], [group_b]”


We are trying to migrate away from observes. Is there any way this code can be called when an event is triggered, say the share interface shows up?

The issue was that the topic wasn’t present when onShow was first fired. See my subsequent commit for a possible solution to this issue. Is there a better/cleaner way to do this?