Merge pull request #80 from ycombinator/x-pack/management/beats

Documents built-in `beats_admin` role

Author: ycombinator

docs/en/stack/security/authorization/built-in-roles.asciidoc

@@ -50,6 +50,10 @@ change between releases.
 NOTE: This role does not provide access to the logstash indices and is not
 suitable for use within a Logstash pipeline.
 
+[[built-in-roles-beats-admin]] `beats_admin` ::
+Grants access to the `.management-beats` index, which contains configuration
+information for the Beats.
+
 [[built-in-roles-beats-system]] `beats_system` ::
 Grants access necessary for the Beats system user to send system-level data
 (such as monitoring) to {es}.