Is your feature request related to a problem? Please describe.
Channels allow the API to set the announcement can this be done with groups

usecase: We use the announcement feature to inform our whole userbase of planned maintenance we then revert this back to whatever it was afterwards we would like this power over private rooms also.

Describe the solution you'd like
add a groups.setAnnouncement endpoint

Describe alternatives you've considered
changing channel to a public room to set the announcement then changing it back but this is really hacky