Check exception class whitelisting with a method

* Move repeated code to a new method
* Add #flatten to the chain to avoid situations where a nested array is
  silently accepted, but exceptions are not passed through

Author: vijoc

lib/jsonapi/acts_as_resource_controller.rb

@@ -179,7 +179,7 @@ def handle_exceptions(e)
       when JSONAPI::Exceptions::Error
         render_errors(e.errors)
       else
-        if JSONAPI.configuration.exception_class_whitelist.any? { |k| e.class.ancestors.include?(k) }
+        if JSONAPI.configuration.exception_class_whitelisted?(e)
           fail e
         else
           internal_server_error = JSONAPI::Exceptions::InternalServerError.new(e)

lib/jsonapi/configuration.rb

@@ -95,6 +95,10 @@ def operations_processor=(operations_processor)
       @operations_processor = JSONAPI::OperationsProcessor.operations_processor_for(@operations_processor_name)
     end
 
+    def exception_class_whitelisted?(e)
+      @exception_class_whitelist.flatten.any? { |k| e.class.ancestors.include?(k) }
+    end
+
     attr_writer :allow_include, :allow_sort, :allow_filter
 
     attr_writer :default_paginator

lib/jsonapi/operations_processor.rb

@@ -92,7 +92,7 @@ def with_default_handling(&block)
       raise e
 
     rescue => e
-      if JSONAPI.configuration.exception_class_whitelist.any? { |k| e.class.ancestors.include?(k) }
+      if JSONAPI.configuration.exception_class_whitelisted?(e)
         raise e
       else
         @request.server_error_callbacks.each { |callback| safe_run_callback(callback, e) }