Restricted indices (currently only .security-6 and .security) are special
internal indices that require setting the `allow_restricted_indices` flag
on every index permission that covers them. If this flag is `false`
(default) the permission will not cover these and actions against them
will not be authorized.
However, the monitoring APIs were the only exception to this rule.
This exception is herein forfeited and index monitoring privileges have to be
granted explicitly, using the `allow_restricted_indices` flag on the permission,
as is the case for any other index privilege.
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