Change log for OPEN_VPN

Date	Changes
2024-11-27	Enchancement - Added Grok patterns to parse unparsed logs. - Mapped "username1" field to "target.user.userid". - Mapped "msg1" field to "metadat.description". - Mapped "metadata.event_type" to "USER_UNCATEGORIZED" when target.user.userid is set. - Mapped "metadata.product_event_type" to "Peer Connection Initiated" for the logs having "Peer Connection Initiated" in the "operation" field.
2023-11-27	Enchancement - Added support for JSON format logs. - Mapped "HOSTNAME" to "principal.hostname". - Mapped "PID" to "principal.process.pid". - Mapped "CMDLINE" to "principal.process.command_line". - Mapped "SYSTEMD_UNIT" to "additional.fields". - Mapped "SYSTEMD_SLICE" to "additional.fields". - Mapped "SYSTEMD_INVOCATION_ID" to "additional.fields". - Mapped "SYSLOG_IDENTIFOER" to "additional.fields". - Mapped "COMM" to "additional.fields". - Added GROK pattern to map "MESSAGE"
2022-04-28	Newly created parser.