[Logstash] Replace the @timestamp with a rsyslog ISO8691 timestamp from Filebeat log lines

Elastic Stack Logstash
3

Hi Badger,

The rsyslog.timestamp is defined by myself in the dissect processor.

processors:
    - dissect:
        tokenizer: "%{rsyslog.timestamp} %{rsyslog.hostname} %{programname}: %{severity} %{swift_logs}"
        field: "message"
        target_prefix: ""

How's right way to assign a field abc.efg to be the @timestamp in logstash?