Description of problem:
The comand for create secret is wrong:
$ oc create secret generic image-registry-private-configuration-user --from-file=KEY1=value1 --from-literal=KEY2=value2 --namespace openshift-image-registry
should be
$ oc create secret generic image-registry-private-configuration-user--from-literal=KEY1=value1 --from-literal=KEY2=value2 --namespace openshift-image-registry in doc:
https://redhat:redhat@docs.openshift.com/container-platform/4.12/registry/configuring-registry-operator.html#registry-operator-config-resources-storage-credentials_configuring-registry-operator