refactor(conf): systemd DynamicUser for slurmrestd

Instead of creating system user and group for slurmrestd, rely of
systemd DynamicUser feature to create the user dynamically when the
service starts.

Author: rezib

conf/roles/slurm/tasks/server.yml

@@ -39,25 +39,6 @@
     state: latest
   when: slurm_with_accounting
 
-# Create slurmrestd system user/group to run slurmrestd with unprivileged user
-# when using TCP/IP socket (ie. not unix socket).
-- name: Create slurmrestd system group
-  ansible.builtin.group:
-    name: slurmrestd
-    gid: "{{ slurmrestd_gid }}"
-  when: slurm_with_jwt
-
-- name: Create slurmrest system user
-  ansible.builtin.user:
-    name: slurmrestd
-    uid: "{{ slurmrestd_uid }}"
-    group: slurmrestd
-    system: yes
-    shell: /sbin/nologin
-    home: /var/spool/slurmrest
-    create_home: no
-  when: slurm_with_jwt
-
 - name: Install slurmrestd
   ansible.builtin.package:
     name: "{{ slurm_emulator | ternary(slurm_emulator_server_packages, slurm_restd_packages) }}"

conf/roles/slurm/templates/slurmrestd.service.j2

@@ -16,6 +16,7 @@ RuntimeDirectoryMode=0755
 ExecStart=/usr/sbin/slurmrestd $SLURMRESTD_OPTIONS {% if not slurm_with_accounting %}-s openapi/slurmctld {% endif %}-a {% if slurm_with_jwt %}rest_auth/jwt{% else %}rest_auth/local{% endif %} [::]:{{ slurm_restd_port }}
 {% endif %}
 {% if slurm_with_jwt %}
+DynamicUser=yes
 User=slurmrestd
 Group=slurmrestd
 {% else %}