Reverse lookup from username to the AccountId that has registered it and the provider of
the username. The owner value should be a key in the UsernameOf map, but it may not if
the user has cleared their username or it has been removed.
Multiple usernames may map to the same AccountId, but UsernameOf will only map to one
primary username.
Reverse lookup from
usernameto theAccountIdthat has registered it and the provider of the username. Theownervalue should be a key in theUsernameOfmap, but it may not if the user has cleared their username or it has been removed.Multiple usernames may map to the same
AccountId, butUsernameOfwill only map to one primary username.