It is using a trigger tripleo::profile::base::keystone::ldap_backend_enable in puppet-tripleo
who will call a define in puppet-keysone ldap_backend.pp.
Given the following environment:
parameter_defaults:
  KeystoneLDAPDomainEnable: true
  KeystoneLDAPBackendConfigs:
    tripleoldap:
      url: ldap://192.0.2.250
      user: cn=openstack,ou=Users,dc=redhat,dc=example,dc=com
      password: Secrete
      suffix: dc=redhat,dc=example,dc=com
      user_tree_dn: ou=Users,dc=redhat,dc=example,dc=com
      user_filter: "(memberOf=cn=OSuser,ou=Groups,dc=redhat,dc=example,dc=com)"
      user_objectclass: person
      user_id_attribute: cn
      user_allow_create: false
      user_allow_update: false
      user_allow_delete: false
  ControllerExtraConfig:
    nova::keystone::authtoken::auth_version: v3
    cinder::keystone::authtoken::auth_version: v3
It would then create a domain called tripleoldap with an LDAP
configuration as defined by the hash. The parameters from the
hash are defined by the keystone::ldap_backend resource in
puppet-keystone.
More backends can be added as more entries to that hash.
This also enables multi-domain support for horizon.
Conflicts:
    puppet/services/keystone.yaml
Closes-Bug: 
1677603
Co-Authored-By: Juan Antonio Osorio Robles <jaosorior@redhat.com>
Depends-On: I1593c6a33ed1a0ea51feda9dfb6e1690eaeac5db
Change-Id: I6c815e4596d595bfa2a018127beaf21249a10643
Signed-off-by: Cyril Lopez <cylopez@redhat.com>
(cherry picked from commit 
347f5434b3e3793b9fdf2a94f49ab7734c5d923b)
--- /dev/null
+# This is an example template on how to configure keystone domain specific LDAP
+# backends. This will configure a domain called tripleoldap will the attributes
+# specified.
+parameter_defaults:
+  KeystoneLDAPDomainEnable: true
+  KeystoneLDAPBackendConfigs:
+    tripleoldap:
+      url: ldap://192.0.2.250
+      user: cn=openstack,ou=Users,dc=tripleo,dc=example,dc=com
+      password: Secrete
+      suffix: dc=tripleo,dc=example,dc=com
+      user_tree_dn: ou=Users,dc=tripleo,dc=example,dc=com
+      user_filter: "(memberOf=cn=OSuser,ou=Groups,dc=tripleo,dc=example,dc=com)"
+      user_objectclass: person
+      user_id_attribute: cn
+      user_allow_create: false
+      user_allow_update: false
+      user_allow_delete: false
 
     description: >
         Cron to purge expired tokens - User
     default: 'keystone'
+  KeystoneLDAPDomainEnable:
+    description: Trigger to call ldap_backend puppet keystone define.
+    type: boolean
+    default: False
+  KeystoneLDAPBackendConfigs:
+    description: Hash containing the configurations for the LDAP backends
+                 configured in keystone.
+    type: json
+    default: {}
+    hidden: true
 
 resources:
 
 
 conditions:
   keystone_fernet_tokens: {equals: [{get_param: KeystoneTokenProvider}, "fernet"]}
+  keystone_ldap_domain_enabled: {equals: [{get_param: KeystoneLDAPDomainEnable}, True]}
 
 outputs:
   role_data:
             keystone::cron::token_flush::maxdelay: {get_param: KeystoneCronTokenFlushMaxDelay}
             keystone::cron::token_flush::destination: {get_param: KeystoneCronTokenFlushDestination}
             keystone::cron::token_flush::user: {get_param: KeystoneCronTokenFlushUser}
+          -
+            if:
+            - keystone_ldap_domain_enabled
+            -
+              tripleo::profile::base::keystone::ldap_backend_enable: True
+              keystone::using_domain_config: True
+              tripleo::profile::base::keystone::ldap_backends_config:
+                get_param: KeystoneLDAPBackendConfigs
+            - {}
 
       step_config: |
         include ::tripleo::profile::base::keystone
           keystone::db::mysql::allowed_hosts:
             - '%'
             - "%{hiera('mysql_bind_host')}"
+        horizon:
+          if:
+          - keystone_ldap_domain_enabled
+          -
+            horizon::keystone_multidomain_support: true
+            horizon::keystone_default_domain: 'Default'
+          - {}
       # Ansible tasks to handle upgrade
       upgrade_tasks:
         - name: Stop keystone service (running under httpd)
 
--- /dev/null
+---
+features:
+  - Add capabilities to configure LDAP backends as for keystone domains.
+    This can be done by using the KeystoneLDAPDomainEnable and
+    KeystoneLDAPBackendConfigs parameters.