Development REST API service

Rails
1

hello, i develop rest api for my project and using grape
https://github.com/intridea/grape

And i have two questions:

  1. For every error i want to have some specific code. Like twillio
    https://www.twilio.com/docs/errors/reference. where should I store
    these
    codes?
  2. How should I organize the work with the codes and grape?

For example:

I have user model

class User < ActiveRecord::Base
validates :phone, presence: true # code 1001
validated :phone, uniqueness: true # code 1002
validates :first_name, presence: true # code 1003
validates :last_name, presence: true #code 1004
end

In grape api i have something like this

post do
authenticated!
user = User.new(params)
if user.save
{ id: user.id }
else
error!({ errors: user.errors }, 422)
end
end

I thought to use the function fail and using Grape rescue_from
generate
response
but I’m not sure that this is true