Sometimes admins will change the LDAP configuration, not realizing
that problems will occur if the user's LDAP identities are not
also updated to use the new provider name. This task will give
admins a single command to run to update identities and will
prevent having to run multiple Rails console queries.
It was previously possible for invalid credential errors to go unnoticed
in this task. Users would believe everything was configured correctly and
then sign in would fail with 'invalid credentials'. This adds a specific
bind check, plus catches errors connecting to the server. Also, specs :)
