Add s-nail package

This includes the /usr/bin/mail command, which is required for Slurm to
send email notifications [1].

[1] https://slurm.schedmd.com/slurm.conf.html#OPT_MailProg

Author: priteau

docs/operations.md

@@ -74,6 +74,7 @@ By default, the following utility packages are installed during the StackHPC ima
 - postfix
 - git
 - latest python version for system (3.6 for for Rocky 8.9 and 3.12 for Rocky 9.4)
+- s-nail
 
 Additional packages can be added during image builds by:
 - adding the `extra_packages` group to the build `inventory_groups` (see

environments/common/inventory/group_vars/all/defaults.yml

@@ -94,6 +94,7 @@ appliances_extra_packages_default:
  - postfix
  - git
  - "{{ 'python36' if ansible_distribution_version == '8.9' else 'python312' }}"
+ - s-nail
 
 appliances_extra_packages_other: []