In our ldap directory in Jira, we have added the property to add automatically users to jira-users group.
We also have added the plugin Service Desk to Jira.
If an user login the first time to the Service Desk portal (example :
https://myJira/servicedesk/customer/user/login) , then no group is added since it is a customer and a customer does not need a license.
But if he tries to go to the Jira Software part (https://myjira/login.jsp) , then he could not login. An administrator has to put him in jira-users group to able his account.
He should be added automatically as the other users who do not login to the service Desk portal.