If you're looking to just assign users from AD to groups within JIRA you can do so via CROWD. You can also review the Default Group Memberships section of the Connecting to an Internal Directory with LDAP Authentication knowledge base article:
Default Group Memberships
This field appears if you check the Copy User on Login box. If you would like users to be automatically added to a group or groups, enter the group name(s) here. To specify more than one group, separate the group names with commas. Each time a user logs in, their group memberships will be checked. If the user does not belong to the specified group(s), their username will be added to the group(s). If a group does not yet exist, it will be added to the internal directory that is using LDAP for authentication.
Please note that there is no validation of the group names. If you mis-type the group name, authorization failures will result – users will not be able to access the applications or functionality based on the intended group name.
In regards to the users not having to login they won't need to login before this takes place.
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