Read only (immutable) relationships

This issue is a (choose one):

• Problem/bug report.
• [ x ] Feature request.
• Request for support. Note: Please try to avoid submitting issues for support requests. Use Gitter instead.

Checklist before submitting:

• I've searched for an existing issue.
• I've asked my question on Gitter and have not received a satisfactory answer.
• I've included a complete bug report template. This step helps us and allows us to see the bug without trying to reproduce the problem from your description. It helps you because you will frequently detect if it's a problem specific to your project.
• The feature I'm asking for is compliant with the JSON:API spec.

Description

Features:

As an engineer I would like to add has_many or has_one relations which are read only. To accomplish this on the current implementation the following code is used in the resource file.

has_many :cars

def cars=(_cars); end

Comienza en la implementación del recurso que gestiona las declaraciones has_many y has_one, usando la definición de recurso de ejemplo como punto de entrada. Sigue cómo se generan o invocan los writers de relaciones y, después, añade compatibilidad declarativa para relaciones de solo lectura y localiza las pruebas de relaciones relevantes para verificar que ya no sea necesario el workaround del setter personalizado.