Add hint to RFC 5424 in log.syslog.severity.name and log.syslog.severity.code

[fgierlinger]

This PR updates the description of log.syslog.severity.name and log.syslog.severity.code to explicitly name the allowed values according to RFC 5424.

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[github-actions]

Documentation changes preview: https://ecs_2291.docs-preview.app.elstc.co/diff

[github-actions]

This PR is stale because it has been open for 60 days with no activity.

[efd6]

Are we limiting to RFC 5424? RFC 3164 has the same values, so we could say "RFC 3164/RFC 5424".

[fgierlinger]

@efd6 RFC 3164 has been obsoleted by RFC 5424

[efd6]

Yeah I was just thinking that if people are reading this and they know that they have syslogs coming in in that format, but are not aware of the fact, they could be confused. We do have data sources that use the BSD format and we support it.

[github-actions]

This PR is stale because it has been open for 60 days with no activity.