* [DOCS] Move security APIs to Elasticsearch Ref
* [DOCS] Update links to security APIs
* [DOCS] Fix link to security APIs
Original commit: elastic/x-pack-elasticsearch@d7a9d3f1ab
Includes:
- Extensive changes to "mapping roles" section
- New section for role mapping API
- Updates to LDAP/AD/PKI realms to refer to API based role mapping
- Updates to LDAP/AD realms: `unmapped_groups_as_roles` only looks at file-based mappings
- Updates to LDAP/AD realms: new setting for "metadata"
Original commit: elastic/x-pack-elasticsearch@6349f665f5
Lisa Cawley
Tim Vernum