Only allow lookups in message, not in parameters.

For example, If someone named "${java:os}", he registered an account, I want to log it.

import org.apache.logging.log4j.LogManager

fun main() {
  val logger = LogManager.getLogger("ww")
  val username = "\${java:os}"
  logger.error("username: {}",username)
} 

I want "username: ${java:os}", but got "username: Mac OS X 10.16, architecture: x86_64-64"

If it is possible, could I have a flag to only lookup in message?