added configuration parameter to swift mailer handler

Author: alsar

DependencyInjection/Configuration.php

@@ -104,6 +104,7 @@ public function getConfigTreeBuilder()
                                 ->end()
                             ->end()
                             ->scalarNode('subject')->end() // swift_mailer and native_mailer
+                            ->scalarNode('content_type')->defaultNull()->end() // swift_mailer
                             ->arrayNode('email_prototype') // swift_mailer
                                 ->canBeUnset()
                                 ->beforeNormalization()

DependencyInjection/MonologExtension.php

@@ -240,6 +240,11 @@ private function buildHandler(ContainerBuilder $container, $name, array $handler
                 $message->addMethodCall('setFrom', array($handler['from_email']));
                 $message->addMethodCall('setTo', array($handler['to_email']));
                 $message->addMethodCall('setSubject', array($handler['subject']));
+
+                if (isset($handler['content_type'])) {
+                    $message->addMethodCall('setContentType', array($handler['content_type']));
+                }
+
                 $messageId = sprintf('%s.mail_prototype', $handlerId);
                 $container->setDefinition($messageId, $message);
                 $prototype = new Reference($messageId);