Integrate with Active Model Attributes

[seanpdoyle]

The schema { ... } interface pre-dates the Active Model Attributes API (defined as early as v5.2.0), but clearly draws inspiration from Active Record's Database Schema and Attribute casting (which was extracted into ActiveModel::Attributes).

However, the type information captured in schema { ... } blocks or assigned as Hash arguments to schema= is purely inert metadata.

Proposal

This commit aims to integrate with ActiveModel::Model and ActiveModel::Attributes. Through the introduction of both modules, subclasses of ActiveResource::Base can benefit from type casting attributes and constructing instances with default values.

This commit makes minimally incremental changes, prioritizing backwards compatibility. The reliance on #respond_to_missing? and #method_missing is left largely unchanged. Similarly, the Schema interface continues to provide metadata about its attributes through the Schema#attr method (instead of reading from
ActiveModel::Attributes#attribute_names or
ActiveModel::Attributes.attribute_types).

API Changes

To cast values to their specified types, declare the Schema with the :cast_values set to true.

class Person < ActiveResource::Base
  schema cast_values: true do
    integer 'age'
  end
end

p = Person.new
p.age = "18"
p.age # => 18

To configure inheriting resources to cast values, set the cast_values class attribute:

class ApplicationResource < ActiveResource::Base
  self.cast_values = true
end

class Person < ApplicationResource
  schema do
    integer 'age'
  end
end

p = Person.new
p.age = "18"
p.age # => 18

To set all resources application-wide to cast values, set config.active_resource.cast_values:

  # config/application.rb
  config.active_resource.cast_values = true

[jlurena]

Is this a draft? Once you are done maybe we can combine both our feature enhancements (mine is here: #409) and create a new major version of this gem.

@rails @byroot thoughts?