Convert attribute and relatioship names to symbols

Fixes issues when strings are provided #1019 & #1032

(cherry picked from commit e6240e0)

Author: lgebhardt

lib/jsonapi/resource.rb

@@ -507,10 +507,12 @@ def attributes(*attrs)
         end
       end
 
-      def attribute(attr, options = {})
+      def attribute(attribute_name, options = {})
+        attr = attribute_name.to_sym
+
         check_reserved_attribute_name(attr)
 
-        if (attr.to_sym == :id) && (options[:format].nil?)
+        if (attr == :id) && (options[:format].nil?)
           ActiveSupport::Deprecation.warn('Id without format is no longer supported. Please remove ids from attributes, or specify a format.')
         end
 
@@ -1041,7 +1043,8 @@ def _add_relationship(klass, *attrs)
         options = attrs.extract_options!
         options[:parent_resource] = self
 
-        attrs.each do |relationship_name|
+        attrs.each do |name|
+          relationship_name = name.to_sym
           check_reserved_relationship_name(relationship_name)
           check_duplicate_relationship_name(relationship_name)
 

test/fixtures/active_record.rb

@@ -1462,12 +1462,12 @@ class PersonResource < PersonResource; end
     class PostResource < PostResource; end
 
     class BookResource < JSONAPI::Resource
-      attribute :title
+      attribute "title"
       attributes :isbn, :banned
 
-      has_many :authors
+      has_many "authors"
 
-      has_many :book_comments, relation_name: -> (options = {}) {
+      has_many "book_comments", relation_name: -> (options = {}) {
         context = options[:context]
         current_user = context ? context[:current_user] : nil
 
@@ -1478,7 +1478,7 @@ class BookResource < JSONAPI::Resource
         end
       }, reflect: true
 
-      has_many :aliased_comments, class_name: 'BookComments', relation_name: :approved_book_comments
+      has_many "aliased_comments", class_name: 'BookComments', relation_name: :approved_book_comments
 
       filters :book_comments
       filter :banned, apply: :apply_filter_banned