Merge branch '5.3' into 5.4

* 5.3:
  Add redirections for deleted pages
  Merge standalone Security component docs with Security guide

Author: javiereguiluz

_build/redirection_map

@@ -532,3 +532,8 @@
 /security/authenticator_manager /security
 /security/multiple_guard_authenticators /security/entry_point
 /security/guard_authentication /security/custom_authenticator
+/components/security/authentication /security#authenticating-users
+/components/security/authorization /security#access-control-authorization
+/components/security/firewall /security#the-firewall
+/components/security/secure_tools /security/passwords
+/components/security /security