Graphiti requires writable id also for relations

graphiti.rb

require 'graphiti'

class User; end
class Post; end

class UserResource < Graphiti::Resource
  attribute :id, :integer_id, writable: false
  has_many :posts
end

class PostResource < Graphiti::Resource
  attribute :id, :integer_id, writable: false
  attribute :title, :string, writable: true
  belongs_to :user
end

params = {
  data: {
    id: 123,
    type: 'posts',
    relationships: {
      user: {
        data: { id: 12, type: 'users' }
      }
    }
  }
}

begin
  resource = PostResource.find(params)
rescue Graphiti::Errors::InvalidRequest => e
  puts e.message
end

# There were one or more errors with your request:
#
# data.attributes.id cannot be written
# included..attributes.id cannot be written