create failing spec for keyword args proxy

when the proxy fails to forward keywoard arguments, the error for
methods that only accept keyword arguments looks like this:

ArgumentError:
  wrong number of arguments (given 1, expected 0)

Author: indirect

elasticsearch-model/spec/elasticsearch/model/proxy_spec.rb

@@ -1,4 +1,4 @@
-# Licensed to Elasticsearch B.V. under one or more contributor
+
 # license agreements. See the NOTICE file distributed with
 # this work for additional information regarding copyright
 # ownership. Elasticsearch B.V. licenses this file to you under
@@ -31,6 +31,10 @@ def bar
         'insta barr'
       end
 
+      def keyword_method(foo: 'default value')
+        foo
+      end
+
       def as_json(options)
         {foo: 'bar'}
       end
@@ -98,7 +102,6 @@ def changes_to_save
   end
 
   context 'when instances are cloned' do
-
     let!(:model) do
       DummyProxyModel.new
     end
@@ -121,4 +124,9 @@ def changes_to_save
       expect(duplicate).to eq(duplicate_target)
     end
   end
+
+  it 'forwards keyword arguments to target methods' do
+    expect(DummyProxyModel.new.__elasticsearch__.keyword_method(foo: 'bar')).to eq('bar')
+  end
+
 end