rename domain and group to align with choice done for heat-operator
This is a follow-up to workload-cluster-operator!1 (comment 1670528876)
With this change the domain and group are changed to have everything under .sylva instead of under gitlab.com.
The result is equivalent to having used:
kubebuilder init --domain sylva --repo sylva-projects/sylva-elements/sylva-units-operator
^^^^^
kubebuilder create api --group unitsoperator --version v1alpha1 --kind SylvaUnitsRelease
^^^^^^^^^^^^^
Edited by Thomas Morin