Configurable shell (nologin) for module service users

[DavidePrincipi]

Allow using /usr/sbin/nologin (or similar) as the shell for module service users in NS8, with an option for admins/devs to revert to /bin/bash if needed.

Proposed solution

• Add a setting to choose the default shell for new module users (e.g. nologin, bash).
• Avoid hardcoding /bin/bash in user creation routines.
• Document the behavior, support process, and possible risks.

Alternative solutions

• Keep /bin/bash as default, let admins change it manually.
• Script to bulk-update user shells on request.

Additional context
Quick tests show no immediate problems with nologin, but support/debug becomes less comfortable (use runagent as root). Consider for security hardening.

See also

• Internal team chat https://mattermost.nethesis.it/nethesis/pl/bgkcwmibiiy67g4f4e5dniuxfw