private KeyPair loadOrCreateDomainKeyPair() throws Exception {
        val acme = casProperties.getAcme();
        return loadOrCreateKeyPair(acme.getDomainKey().getLocation().getFile());
    }
Loads a domain key pair. If the file does not exist,
a new key pair is generated and saved.

@return Domain {@link KeyPair}.
support/cas-server-support-acme/src/main/java/org/apereo/cas/acme/DefaultAcmeCertificateManager.java