Remove RABL remnants

RABL was removed from the project on version 2.4.0 (See solidusio#2147 solidusio#2146).
This updates the responder template to match with Jbuilder and updates
the README file.

api/README.md

@@ -1,6 +1,6 @@
 # solidus_api
 
-API contains the controllers and rabl views implementing the REST API of
+API contains the controllers and Jbuilder views implementing the REST API of
 Solidus.
 
 ## Testing

api/lib/spree/api/responders.rb

@@ -1,13 +1,13 @@
 # frozen_string_literal: true
 
 require 'responders'
-require 'spree/api/responders/rabl_template'
+require 'spree/api/responders/jbuilder_template'
 
 module Spree
   module Api
     module Responders
       class AppResponder < ActionController::Responder
-        include RablTemplate
+        include JbuilderTemplate
       end
     end
   end

api/lib/spree/api/responders/rabl_template.rb → api/lib/spree/api/responders/jbuilder_template.rb

@@ -3,7 +3,7 @@
 module Spree
   module Api
     module Responders
-      module RablTemplate
+      module JbuilderTemplate
         def to_format
           if template
             render template, status: options[:status] || 200

api/spec/requests/rabl_cache_spec.rb → api/spec/requests/jbuilder_cache_spec.rb

@@ -2,7 +2,7 @@
 
 require 'spec_helper'
 
-describe "Rabl Cache", type: :request, caching: true do
+describe "Jbuilder Cache", type: :request, caching: true do
   let!(:user)  { create(:admin_user) }
 
   before do
@@ -11,7 +11,7 @@
     expect(Spree::Product.count).to eq(1)
   end
 
-  it "doesn't create a cache key collision for models with different rabl templates" do
+  it "doesn't create a cache key collision for models with different jbuilder templates" do
     get "/api/variants", params: { token: user.spree_api_key }
     expect(response.status).to eq(200)