Update the cookbook about invitation to make it work
Update the cookbook about invitation to make it work

findOneBy is not able to search by the inverse side of a one-to-one
relation. So the implementation needs to use a DQL query instead.
This also gets rid of the bidirectional relation in favor of an
unidirectional one as the inverse side is not necessary in this snippet.

XWB/FOSUserBundle,XWB/FOSUserBundle,FriendsOfSymfony/FOSUserBundle