Arvados

Make the multi-tenant case work better:

In the mode where users are not readable by "All users" by default (and therefore no one is "opted in" to being visible), add a feature where you can create a group and then send an send an "invite" or "friend request" link to someone, when they click on it and approve the connection, they are added to the group so that they are mutually visible to the group without being being required to be visible to the entire instance.