Add the ability to collaborate with other Fellow workspaces without needing to join their workspace as a guest user with guest user capabilities.

"I open a stream of one repeating meeting -> I can ask outside partners to collaborate on it -> my admin has to approve this -> their admin has to approve this -> our stream becomes shared where both teams are treated as equals (only in this stream).

This could be paired with a Slack integration, where Slack allows for collaborative spaces between two companies - so Fellow could utilize that feature and space as well."