An ApplicationListener that saves application PID into file. This application
listener will be triggered exactly once per JVM, and the file name can be overridden at
runtime with a System property or environment variable named "PIDFILE" (or "pidfile")
or using a spring.pid.file property in the Spring Environment.
If PID file can not be created no exception is reported. This behavior can be changed
by assigning true to System property or environment variable named
PID_FAIL_ON_WRITE_ERROR (or "pid_fail_on_write_error") or to
spring.pid.fail-on-write-error property in the Spring Environment.