title: JsonTemplateLayout - eventTemplate - missing values
body: <p>I've implemented log4j2:2.1.2.RELEASE with JsonTemplateLayout.eventTemplate and found some missing values such as line_number. Is there anything that I need to set up separately on the application code?</p>
  <p>currently,
  timestamp, level, host-name, mdc, thread-name, logger-name, exception, message, version look ok.
  class, method, line_number, and file are missing.</p>
  <p>Thanks!</p>