include both type and message when inheriting field-level errors

[aaronrosenthal]

Include both type and message when inheriting field-level errors.

This can be useful in situations where we might want to query the errors without having to consider the full message. For example:

begin
  ::SignupOp.submit!(email: nil)
rescue Subroutine::Failure => e
  if e.record.errors.added?(:email, :blank)
    # some special handling of the error here...
  end
end