Add support for calendar_interval to DateHistogram (#1044)

[DSL] Add support for calendar_interval and fixed_interval to DateHistogram

Author: tmaier

lib/elasticsearch/dsl/search/aggregations/date_histogram.rb

@@ -39,6 +39,8 @@ class DateHistogram
 
           option_method :field
           option_method :interval
+          option_method :fixed_interval
+          option_method :calendar_interval
           option_method :pre_zone
           option_method :post_zone
           option_method :time_zone

spec/elasticsearch/dsl/search/aggregations/date_histogram_spec.rb

@@ -58,6 +58,28 @@
       end
     end
 
+    describe '#fixed_interval' do
+
+      before do
+        search.fixed_interval('bar')
+      end
+
+      it 'applies the option' do
+        expect(search.to_hash[:date_histogram][:foo][:fixed_interval]).to eq('bar')
+      end
+    end
+
+    describe '#calendar_interval' do
+
+      before do
+        search.calendar_interval('bar')
+      end
+
+      it 'applies the option' do
+        expect(search.to_hash[:date_histogram][:foo][:calendar_interval]).to eq('bar')
+      end
+    end
+
     describe '#pre_zone' do
 
       before do