Monkey patch ES gem to handle v7 API total count

This is due to the breaking change introduced in ES7
https://www.elastic.co/guide/en/elasticsearch/reference/current/breaking-changes-7.0.html#hits-total-now-object-search-response
. This can be handled by the v7 client gem but since our main target is
ES6 for now we will just monkey patch the gem with this fix. When we
remove support for ES6 or use the ES7 gem and default to supporting ES7
then we can remove it.

config/initializers/elastic_client_setup.rb

@@ -10,6 +10,7 @@ Gitlab.ee do
   ### Monkey patches
 
   Elasticsearch::Model::Response::Records.prepend GemExtensions::Elasticsearch::Model::Response::Records
+  Elasticsearch::Model::Response::Results.prepend GemExtensions::Elasticsearch::Model::Response::Results
   Elasticsearch::Model::Adapter::Multiple::Records.prepend GemExtensions::Elasticsearch::Model::Adapter::Multiple::Records
   Elasticsearch::Model::Indexing::InstanceMethods.prepend GemExtensions::Elasticsearch::Model::Indexing::InstanceMethods
   Elasticsearch::Model::Adapter::ActiveRecord::Importing.prepend GemExtensions::Elasticsearch::Model::Adapter::ActiveRecord::Importing

ee/lib/gem_extensions/elasticsearch/model/response/results.rb

+# frozen_string_literal: true
+
+module GemExtensions
+  module Elasticsearch
+    module Model
+      module Response
+        module Results
+          # Handle ES7 API where total is returned as an object. This
+          # change is taken from the V7 gem
+          # https://github.com/elastic/elasticsearch-rails/commit/9c40f630e1b549f0b7889fe33dcd826b485af6fc
+          # and can be removed when we upgrade the gem to V7
+          def total
+            if response.response['hits']['total'].respond_to?(:keys)
+              response.response['hits']['total']['value']
+            else
+              response.response['hits']['total']
+            end
+          end
+        end
+      end
+    end
+  end
+end