Describe the bug
Staying on the attributeMapper inside the SamrpLDAPGroupStore configuration isn't anymore available due to #1989
In the init.crn the ldap-search require that the contextMapper is not null ! and from the groupStore class we can't have the atrributeMapper defined at the same time than the contextMapper.

To Reproduce
Steps to reproduce the behavior:

1. configure the SamrLdapGroupStrore with the attributemapper only.
2. deploy and restart the tomcat
3. connect to uPortal and watch logs - users can't connect

Expected behavior
Cernunnos lib seems buggy and should manage correctly things !

Stacktrace

ERROR [SmartLdap Refresh Worker] o.a.p.g.s.SmartLdapGroupStore 2020-08-18 11:15:54,835 - SmartLdapGroupStore failed to build the groups tree
org.danann.cernunnos.ManagedException: The Cernunnos Runtime encountered an error:
Origin Document: file:/opt/webapps/uPortal/WEB-INF/classes/org/apereo/portal/groups/smartldap/init.crn
Source: /with-attribute/ldap-search/@context-mapper
Entity Name: ${org.danann.cernunnos.AttributePhrase}
at org.danann.cernunnos.runtime.RuntimePhraseDecorator.evaluate(RuntimePhraseDecorator.java:91)
at org.danann.cernunnos.runtime.ConcatenatingPhrase.evaluate(ConcatenatingPhrase.java:77)
at org.danann.cernunnos.runtime.RuntimeReagentDecorator.evaluate(RuntimeReagentDecorator.java:71)
at org.danann.cernunnos.ldap.SearchTask.perform(SearchTask.java:203)
at org.danann.cernunnos.runtime.RuntimeTaskDecorator.perform(RuntimeTaskDecorator.java:77)
at org.danann.cernunnos.AbstractContainerTask.performSubtasks(AbstractContainerTask.java:148)
at org.danann.cernunnos.AbstractContainerTask.performSubtasks(AbstractContainerTask.java:123)
at org.danann.cernunnos.core.SetAttributeTask.perform(SetAttributeTask.java:66)
at org.danann.cernunnos.runtime.RuntimeTaskDecorator.perform(RuntimeTaskDecorator.java:77)
at org.danann.cernunnos.runtime.ScriptRunner$TaskDecorator.perform(ScriptRunner.java:436)
at org.danann.cernunnos.runtime.ScriptRunner.run(ScriptRunner.java:288)
at org.danann.cernunnos.runtime.ScriptRunner.run(ScriptRunner.java:225)
at org.apereo.portal.groups.smartldap.SmartLdapGroupStore.buildGroupsTree(SmartLdapGroupStore.java:731)
at org.apereo.portal.groups.smartldap.SmartLdapGroupStore.access$200(SmartLdapGroupStore.java:57)
at org.apereo.portal.groups.smartldap.SmartLdapGroupStore$2.run(SmartLdapGroupStore.java:645)
Caused by: java.lang.IllegalArgumentException: The specified attribute is not defined: contextMapper

Platform:

• uPortal Version: uPortal 5.8.2

Additional things
It may be great to watch on moving from cernnunos which is old and not really used now to a groovy script, what do you think ?