Revert "Make fetchable_fields more like other field overrides"

This reverts commit cdc5ef0.

Author: reidab

README.md

@@ -188,7 +188,7 @@ end
 ##### Fetchable Attributes
 
 By default all attributes are assumed to be fetchable. The list of fetchable attributes can be filtered by overriding
-the `self.fetchable_fields` method.
+the `fetchable_fields` method.
 
 Here's an example that prevents guest users from seeing the `email` field:
 
@@ -198,7 +198,7 @@ class AuthorResource < JSONAPI::Resource
   model_name 'Person'
   has_many :posts
 
-  def self.fetchable_fields(context)
+  def fetchable_fields
     if (context[:current_user].guest)
       super - [:email]
     else

lib/jsonapi/resource.rb

@@ -105,8 +105,9 @@ def replace_fields(field_data)
       end
     end
 
+    # Override this on a resource instance to override the fetchable keys
     def fetchable_fields
-      self.class.fetchable_fields(context)
+      self.class.fields
     end
 
     # Override this on a resource to customize how the associated records
@@ -440,11 +441,6 @@ def method_missing(method, *args)
       end
       # :nocov:
 
-      # Override in your resource to filter the fetchable keys
-      def fetchable_fields(_context = nil)
-        fields
-      end
-
       # Override in your resource to filter the updatable keys
       def updatable_fields(_context = nil)
         _updatable_relationships | _attributes.keys - [:id]