i18n: fix enum values for Dossier.state

According to Rails i18n guide, enum values should be localized
as `<model>/<enum>`, not as sub-values to the attribute.

This fixes an exception in administrate when displaying a Dossier
in the Manager.

Note: we need to change the way GraphQL attributes are generated, because
`AASM::Core::State#display_name` doesn’t honor the `model/attribute.value`
convention (and instead tries to localize as `model.attribute/value`).
So instead we lookup the localized name using ActiveRecord.

app/helpers/dossier_helper.rb

@@ -51,7 +51,7 @@ module DossierHelper
 
   def dossier_display_state(dossier_or_state, lower: false)
     state = dossier_or_state.is_a?(Dossier) ? dossier_or_state.state : dossier_or_state
-    display_state = I18n.t(state, scope: [:activerecord, :attributes, :dossier, :state])
+    display_state = Dossier.human_attribute_name("state.#{state}")
     lower ? display_state.downcase : display_state
   end