OsInviteToGroup

The object must have a group set and can not be group owned.
The object owner must have the right to invite new users to the group the object is set to.
The user with the given key has to be online in that region.
The user gets a normal group invitation, showing the owner of the object as sender. The invitation can be accepted or rejected and the user can open the corresponding group window.

Returns TRUE, if the invitation could be sent, otherwise FALSE.
Since version 0.9.2, it will return TRUE (ie 1) if user is already member of the group.

This function may fail during a short time, after changing group roles