anchor.diff:  
   `sslTrustAllCertificates`::
       Skip SSL server certificate validation; default false (*optional*)
  +
  +
  +=== Customize GELF messages
  +
  +If you want to customize the GELF messages sent by the appender, you can
  +replace the class that converts log events to GELF messages with your own
  +implementation. Define a class implementing the `GelfMessageFactory`
  +interface. Alternatively, you may extend the `DefaultGelfMessageFactory`
  +class, which implements this interface.
  +
  +Configure the custom GELF message factory in the appender:
  +[source,xml]
  +--
  +<appender name="GRAYLOG2" class="com.github.pukkaone.gelf.logback.GelfAppender">
  +  ...
  +  <marshaller class="com.example.MyGelfMessageFactory">
  +    <mdcTimestampProperty>ReceivedDateTime</mdcTimestampProperty>
  +  </marshaller>
  +  ...
  +</appender>
  +--
  
positive.code: <dependency>
    <groupId>com.github.pukkaone</groupId>
    <artifactId>logback-gelf</artifactId>
    <version>1.1.6</version>
  </dependency>
  --
  
  
negative.code:   <facility>gelf-java</facility>
    <additionalField>application=MyApplication</additionalField>
    <additionalField>environment=development</additionalField>
  </appender>
  --
  
  