User Invitation/Poking a user to a topic is now live!

[techAPJ (Arpit Jalan)]

@fantasticfears

The notification text doesn’t make sense when you invite a username

@codinghorror

for SSO users it is safe to enable just the username invite ability

@sam

First thing that needs fixing is invite/add into message for sso

Fixed

FEATURE: support inviting existing users to topic and message when SSO is enabled