when using field aliasing, I think the correct would be defining the index using the alias name, but now only work if using the field real name

this does not work (does not create index to field "a"):
field :a, as: :authentication_token
index(

{ authentication_token: 1 }

,

{ unique: true }

)

this works:
field :a, as: :authentication_token
index(

{ a: 1 }

,

{ unique: true }

)