Add support for setting minimum UID for users defined via basic_users

[sjpb]

Adds a variable basic_users_uid_min to the basic_users role, and checks that the UIDs specified for normal (i.e. non-system) users are above this. This makes it harder to accidently mix interactive users defined via the role in with the autogenerated UIDs for users installed for services etc.

Note that testing showed setting UID_MIN in /etc/login.defs did not prevent users being created with incorrect UIDs - it simply prints a warning. Hence this is implemented as an assert.

Requires image build as role copied into basic_users.

[sjpb]

Image build: https://github.com/stackhpc/ansible-slurm-appliance/actions/runs/25721747044

[sjpb]

Above image build failing repeatedly on RL8 for openhpc.

edit: ok launched builder manually, hits

[root@slurm-rl8-test-260512-1329-397bd574 rocky]# dnf list gcc
OpenHPC 52 B/s | 50 B 00:00
Errors during downloading metadata for repository 'OpenHPC':

• Status code: 403 for https://ark.stackhpc.com/pulp/content/OpenHPC/2/EL_8/20241218T154614/repodata/repomd.xml (IP: 45.135.56.128)
  Error: Failed to download metadata for repo 'OpenHPC': Cannot download repomd.xml: Cannot download repodata/repomd.xml: All mirrors were tried

But:

$ curl https://$ARKUSER:$ARKPW@ark.stackhpc.com/pulp/content/OpenHPC/2/EL_8/20241218T154614/repodata/repomd.xml
302: Found

So have we lost auth?? Yes we have:

[root@slurm-rl8-test-260512-1329-397bd574 rocky]# grep password /etc/yum.repos.d/OpenHPC.repo 
password = 
password = 

edit: not a fair test, local environment not set up to inject ark creds - will have to launch a CI build with no cleanup

[sjpb]

image builds https://github.com/stackhpc/ansible-slurm-appliance/actions/runs/25739548617 - should not get cleaned up on failure

Turns out it was an infra problem, new Ark certs didn't have an intermediary which RL8 required. Fixed.

[sjpb]

Image build: https://github.com/stackhpc/ansible-slurm-appliance/actions/runs/25793029656

[wtripp180901]

LGTM