This commit documents the backup and restore of a cluster's
security configuration.
It is not possible to only backup (or only restore) security
configuration, independent to the rest of the cluster's conf,
so this describes how a full configuration backup&restore
will include security as well. Moreover, it explains how part
of the security conf data resides on the special .security
index and how to backup that using regular data snapshot API.
Co-Authored-By: Lisa Cawley <lcawley@elastic.co>
Co-Authored-By: Tim Vernum <tim@adjective.org>
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