Establish the Security Model for Cassandra

patch by Francisco Guerrero; reviewed by Stefan Miklosovic for CASSANDRA-21392

Author: frankgh

doc/modules/cassandra/pages/reference/index.adoc

@@ -6,4 +6,5 @@
 * xref:reference/native-protocol.adoc[Native Protocol specification]
 * xref:reference/sai-virtual-table-indexes.adoc[SAI virtual table]
 * xref:reference/static.adoc[Static columns]
-* xref:reference/vector-data-type.adoc[Vector data type]
+* xref:reference/vector-data-type.adoc[Vector data type]
+* xref:reference/security-model.adoc[Security Model]