Define respond_to? on RecordRef to match method_missing behavior

`RecordRef`s often include a name, which allows access via
`method_missing` by calling `record_ref.name`, however if no referenced
record is assigned, you'll still get a `RecordRef` instance, it just
wont have any fields, so `record_ref.name` raised a `NoMethodError`, but
if you checked for the field first via `record_ref.respond_to?(:name)`,
it'd be falsey regardless of whether the field existed or not.

Defining `respond_to?` in good practice alongside `method_missing`.
Ideally, `respond_to_missing?` would be used instead, as that enables
access to the method like `record_ref.method(:name)`, however I kept
with `respond_to?` to match `CustomFieldList`.

`CustomRecordRef` also uses `method_missing`, however there's no specs
and I'm not familiar with that record, so I left it alone.

HISTORY.md

@@ -6,6 +6,7 @@
 
 ### Fixed
 * Revert recent proxy changes which breaks proxy usage by @andrewdicken-stripe in https://github.com/NetSweet/netsuite/pull/579
+* Define `respond_to?` on `RecordRef` to match `method_missing` behavior (#608)
 
 ### Breaking Changes
 

lib/netsuite/records/record_ref.rb

@@ -33,6 +33,11 @@ def method_missing(m, *args, &block)
         end
       end
 
+      def respond_to?(m, include_private = false)
+        return true if attributes.keys.map(&:to_sym).include?(m.to_sym)
+        super
+      end
+
     end
   end
 end

spec/netsuite/records/record_ref_spec.rb

@@ -40,8 +40,16 @@
 
     context 'readers' do
       it 'can take on arbitrary attributes into itself on initialization' do
+        expect(record_ref).to respond_to(:name)
+        expect(record_ref).to respond_to('name')
         expect(record_ref.name).to eql('This is a record_ref')
+
+        expect(record_ref).to respond_to(:banana)
+        expect(record_ref).to respond_to('banana')
         expect(record_ref.banana).to eql('for monkeys')
+
+        expect(record_ref).to_not respond_to(:non_existant_field)
+        expect(record_ref).to_not respond_to('non_existant_field')
       end
     end
   end