Cannot use a custom certificate for oauth-openshift route in OpenShift 4

Issue

• Some companies have a restricted policy about using wildcard certificates.
• OAuth route (like oauth-openshift.apps.mycluster.domain.tld) uses the default wildcard certificate.
• Editing the secret v4-0-config-system-router-certs in openshift-authentication namespace by replacing the certificate with a customized one works but the change is reverted by the Authentication Operator.