I have set up a Yammer group for my team and I have added most of them to the group manually. However the rest haven't yet activated their O365 accounts so I can't add them right now. I want the group to be private, but I want the rest to be able to join without me having to approve them.
When a user requests to join a group all admins of the group get a notification in their Yammer notifications list and an email in their inbox. There is clearly a trigger there already - it would be nice if that trigger could be exposed for Flow too. You would need to also expose an action to approve a group join request, and a condition to check against a provided list of account names that don't already exist in O365, perhaps identified by email address.