In openstreetmap/openstreetmap-website#5242, we were wondering why i18n-tasks is reporting a model validation message as unused, although it is being referenced from a model:

 validates :subject, :uniqueness => { :scope => :owner_id, :message => :is_already_muted }

At the moment, we need to add the error string to the i18n-tasks.yml file to ignore the warning:

ignore_unused:
  'activerecord.errors.models.user_mute.is_already_muted'

I'm not sure if we're missing something here. Is this the recommended approach to address model validation messages?