Currently if an instructor tries to delete the only remaining roster attached to a course site (and there are no manually enrolled users with the maintain role), the instructor will receive an error message:
Alert: The site has to have at least one user with role Instructor.
This has been reported as a pain point for users, as they have to remember to add a roster before they can remove the last roster, or enroll another user as a non-provided maintain roll. This also allows them to utilize the site without having a roster attached.
The linked PR introduces a new sakai.property (site.setup.allowDelLastRoster) to control this behaviour so that the user is automatically enrolled as a non-provided maintainer role in the course site so that they are able to delete the last roster attached to a site. The new configuration option defaults to false to preserve OOTB functionality.
An instructor creates a course site with the intentions of building course materials prior to the course starting date. She does not want anyone to be able to access the site before she's finished creating all the necessary material. She unpublishes the site with this intention. However, the instructor realizes that anyone who is granted the "view unpublished sites" permission can still access the site. As a workaround, she attempts to temporarily remove the roster from the site until she's finished, but receives an error stating the action would leave no users remaining in the site with the Instructor role.
She attempts to add her own user to the site as the Instructor role, but is presented with an error because she already exists in the roster. She then manually adds another user to the site in the Instructor role, and then deletes the roster. This results in the roster being removed from the site, and subsequently (and unintentionally) she's lost access to the site herself. Support call(s) ensue...
Enabling this feature may have legal implications, depending on your local privacy laws (FERPA, FIPPA, GDPR, etc.). For example:
If SIS data integration is the source of authority, it's possible that the instructor who deletes the last roster in a site may actually be removed from the roster in the SIS data sometime after the roster was removed from the site. Having the roster detached from the site prevents this update from happening, and may as a result grant the instructor undue access to course materials, grades, etc. which the institution has effectively tried to revoke.