Provide your slack app with a stream of all activity in Slack for conversations and people it can see
rtm:stream is a scope allowing access to the Real Time Messaging API and rtm.connect.
This scope is like an illusion.
It cannot be requested directly, but is virtually imbued upon tokens associated with specific scopes.
Typically granted to bot user tokens produced while requesting the bot scope.
rtm:stream is also applied to user tokens rewarded after asking for the legacy client scope, though it's a deprecated approach.