feat: add extended settings mapping

fix: gravitee-io/issues#4615

gravitee-gateway-standalone/gravitee-gateway-standalone-distribution/src/main/resources/config/gravitee.yml

@@ -166,6 +166,7 @@ reporters:
 #    template_mapping:
 #      path: ${gravitee.home}/config/reporter/elasticsearch/templates
 #      extended_request_mapping: request.ftl
+#      extended_settings: settings.ftl
 
 # Gateway service configurations. Provided values are default values.
 # All services are enabled by default. To stop one of them, you have to add the property 'enabled: false' (See the