Add support for headers in native mailer

The native mailer is able to have additional headers, but it
wasn't possible to give it any headers in the configuration.
Swift mailer may have a content_type key but not native mailer.

A new "headers" key is now allowed in the handler configuration, so a
list of headers may be given to the handler. Only native mailer supports
it.

Related to #272

Author: nalysius

DependencyInjection/Configuration.php

@@ -175,6 +175,7 @@
  *   - subject: string
  *   - [level]: level name or int value, defaults to DEBUG
  *   - [bubble]: bool, defaults to true
+ *   - [headers]: optional array containing additional headers
  *
  * - socket:
  *   - connection_string: string
@@ -594,6 +595,10 @@ public function getConfigTreeBuilder()
                             ->end()
                             ->scalarNode('subject')->end() // swift_mailer and native_mailer
                             ->scalarNode('content_type')->defaultNull()->end() // swift_mailer
+                            ->arrayNode('headers') // native_mailer
+                                ->canBeUnset()
+                                ->scalarPrototype()->end()
+                            ->end()
                             ->scalarNode('mailer')->defaultValue('mailer')->end() // swift_mailer
                             ->arrayNode('email_prototype') // swift_mailer
                                 ->canBeUnset()

DependencyInjection/MonologExtension.php

@@ -540,6 +540,9 @@ private function buildHandler(ContainerBuilder $container, $name, array $handler
                 $handler['level'],
                 $handler['bubble'],
             ));
+            if (!empty($handler['headers'])) {
+                $definition->addMethodCall('addHeader', $handler['headers']);
+            }
             break;
 
         case 'socket':

Resources/config/schema/monolog-1.0.xsd

@@ -88,6 +88,7 @@
         <xsd:attribute name="content-type" type="xsd:string" />
         <xsd:attribute name="webhook-url" type="xsd:string" />
         <xsd:attribute name="slack-team" type="xsd:string" />
+        <xsd:attribute name="headers" type="headers" />
     </xsd:complexType>
 
     <xsd:simpleType name="level">
@@ -186,4 +187,10 @@
         </xsd:choice>
         <xsd:attribute name="code" type="xsd:integer" />
     </xsd:complexType>
+
+    <xsd:complexType name="headers">
+        <xsd:choice minOccurs="0" maxOccurs="unbounded">
+            <xsd:element name="header" type="xsd:string" />
+        </xsd:choice>
+    </xsd:complexType>
 </xsd:schema>