[MODEL] Delegate max_pages method properly for Kaminari's next_page

Delegate `max_pages` to `Elasticsearch::Model::Response::Results` and `Elasticsearch::Model::Response::Response`, in order to  Kaminari method `next_page` work

Closes elastic#452

Author: Glauber Campinho

elasticsearch-model/lib/elasticsearch/model/response/pagination.rb

@@ -20,8 +20,8 @@ def self.included(base)
             Elasticsearch::Model::Response::Results.__send__ :include, ::Kaminari::PageScopeMethods
             Elasticsearch::Model::Response::Records.__send__ :include, ::Kaminari::PageScopeMethods
 
-            Elasticsearch::Model::Response::Results.__send__ :delegate, :limit_value, :offset_value, :total_count, to: :response
-            Elasticsearch::Model::Response::Records.__send__ :delegate, :limit_value, :offset_value, :total_count, to: :response
+            Elasticsearch::Model::Response::Results.__send__ :delegate, :limit_value, :offset_value, :total_count, :max_pages, to: :response
+            Elasticsearch::Model::Response::Records.__send__ :delegate, :limit_value, :offset_value, :total_count, :max_pages, to: :response
 
             base.class_eval <<-RUBY, __FILE__, __LINE__ + 1
               # Define the `page` Kaminari method

elasticsearch-model/test/unit/response_pagination_kaminari_test.rb

@@ -194,6 +194,17 @@ def self.document_type; 'bar'; end
 
         assert_equal 5, @response.page(5).results.current_page
       end
+
+      should "return previous page and next page" do
+        assert_equal nil, @response.page(1).results.prev_page
+        assert_equal 2, @response.page(1).results.next_page
+
+        assert_equal 3, @response.page(4).results.prev_page
+        assert_equal nil, @response.page(4).results.next_page
+
+        assert_equal 2, @response.page(3).results.prev_page
+        assert_equal 4, @response.page(3).results.next_page
+      end
     end
 
     context "records" do
@@ -207,6 +218,17 @@ def self.document_type; 'bar'; end
 
         assert_equal 5, @response.page(5).records.current_page
       end
+
+      should "return previous page and next page" do
+        assert_equal nil, @response.page(1).records.prev_page
+        assert_equal 2, @response.page(1).records.next_page
+
+        assert_equal 3, @response.page(4).records.prev_page
+        assert_equal nil, @response.page(4).records.next_page
+
+        assert_equal 2, @response.page(3).records.prev_page
+        assert_equal 4, @response.page(3).records.next_page
+      end
     end
   end
 
@@ -371,6 +393,17 @@ def self.document_type; 'bar'; end
 
         assert_equal 5, @response.page(5).results.current_page
       end
+
+      should "return previous page and next page" do
+        assert_equal nil, @response.page(1).results.prev_page
+        assert_equal 2, @response.page(1).results.next_page
+
+        assert_equal 3, @response.page(4).results.prev_page
+        assert_equal nil, @response.page(4).results.next_page
+
+        assert_equal 2, @response.page(3).results.prev_page
+        assert_equal 4, @response.page(3).results.next_page
+      end
     end
 
     context "records" do
@@ -384,6 +417,17 @@ def self.document_type; 'bar'; end
 
         assert_equal 5, @response.page(5).records.current_page
       end
+
+      should "return previous page and next page" do
+        assert_equal nil, @response.page(1).records.prev_page
+        assert_equal 2, @response.page(1).records.next_page
+
+        assert_equal 3, @response.page(4).records.prev_page
+        assert_equal nil, @response.page(4).records.next_page
+
+        assert_equal 2, @response.page(3).records.prev_page
+        assert_equal 4, @response.page(3).records.next_page
+      end
     end
   end
 end