[enhancement]: rh_subscription needs releasever field.

[StHeck]

Enhancement

Currently there is no way to set the release version in Red Hat subscription manager in cloud-init user-data rh_subscription.

This will cause package_upgrade: true and package_update: true to update to the latest version of RHEL, which may not be desired in some situations.

[mostafaCamel]

In /etc/cloud/cloud.cfg of a RHEL VM, the package_update_upgrade_install module will be executed well after the rh_subscription module so changes to rh_subscription will fix the issue

For local development steps with RHEL VMs, check these 2 comments: #6292 (comment) and #6292 (comment)

[mostafaCamel]

Local development steps specific to this issue

One time after the inital boot in the VM

Modify config/schemas/schema-cloud-config-v1.json config/cc_rh_subscription.py util.py
under /usr/lib/python3.12/site-packages/cloudinit (and not the usual /usr/lib/python/dist-packages/cloudinit of debian distros) with my code changes

For valid releases to choose from, check sudo subscription-manager release --list (with the system registered)

The steps in the VM to loop through when doing experiments on cloud-config

sudo subscription-manager release --show
sudo subscription-manager unregister
ls /var/cache/{dnf,yum}
#Modify the cloud-config in /var/lib/cloud/instance/cloud-config.txt
sudo cloud-init single --name cc_rh_subscription --frequency always
sudo subscription-manager release --show
ls /var/cache/{dnf,yum} 

[mostafaCamel]

Created a pull request #6347 . The general idea is to execute sudo subscription-manager release --set=<releasever> then to delete the cache files /var/cache/{dnf,yum} as suggested in https://access.redhat.com/solutions/238533

We are not statically checking that the schema key is a valid release (i.e. that it is in the output of sudo subscription-manager release --list because some releases require some repo enablement first , and the repo enablement step occurs only after the static schema keys checking + anyways this will be caught during sudo subscription-manager release --set=<releasever>