Fix the multibyte config is not properly configured

lib/jenkins_api_client/client.rb

@@ -403,11 +403,11 @@ def get_config(url_prefix)
     # @return [String] Response code returned from Jenkins
     #
     def post_config(url_prefix, xml)
-      post_data(url_prefix, xml, 'application/xml')
+      post_data(url_prefix, xml, 'application/xml;charset=UTF-8')
     end
 
     def post_json(url_prefix, json)
-      post_data(url_prefix, json, 'application/json')
+      post_data(url_prefix, json, 'application/json;charset=UTF-8')
     end
 
     def post_data(url_prefix, data, content_type)

spec/unit_tests/client_spec.rb

@@ -195,6 +195,31 @@
           @client.respond_to?(:post_config).should be_true
           @client.method(:post_config).parameters.size.should == 2
         end
+
+        it "sets the content type with charset as UTF-8 for the multi-byte content" do
+          url_prefix   = '/prefix'
+          xml          = '<dummy>dummy</dummy>'
+          content_type = 'application/xml;charset=UTF-8'
+
+          expect(@client).to receive(:post_data).with(url_prefix, xml, content_type)
+          @client.post_config(url_prefix, xml)
+        end
+      end
+
+      describe "#post_json" do
+        it "is defined and should accept url_prefix and json" do
+          @client.respond_to?(:post_json).should be_true
+          @client.method(:post_json).parameters.size.should == 2
+        end
+
+        it "sets the content type with charset as UTF-8 for the multi-byte content" do
+          url_prefix   = '/prefix'
+          json         = '{ "dummy": "dummy" }'
+          content_type = 'application/json;charset=UTF-8'
+
+          expect(@client).to receive(:post_data).with(url_prefix, json, content_type)
+          @client.post_json(url_prefix, json)
+        end
       end
 
       describe "#get_jenkins_version" do