log(logLine, callback) {
    const metadata = this.agent.getLinkingMetadata(true)
    const formattedLine = reformatLogLine(logLine, metadata)
    this.agent.logs.add(formattedLine)
    callback()
  }
Executed on every log line. We will get the linking metadata
and add this, along with reformatting of timestamp and error
to a copy of the log line

@param {object} logLine a winston log line
@param {Function} callback callback to invoke once we are done