Reverse lookup from username to the AccountId that has registered it. The value should
be a key in the IdentityOf map, but it may not if the user has cleared their identity.
Multiple usernames may map to the same AccountId, but IdentityOf will only map to one
primary username.
Reverse lookup from
usernameto theAccountIdthat has registered it. The value should be a key in theIdentityOfmap, but it may not if the user has cleared their identity.Multiple usernames may map to the same
AccountId, butIdentityOfwill only map to one primary username.