fix(auth): treat empty allowedEmailRegistrationDomains as no restrictions

Author: aji-aju

openmetadata-service/src/main/java/org/openmetadata/service/security/AuthenticationCodeFlowHandler.java

@@ -926,6 +926,7 @@ private User getOrCreateOidcUser(String userName, String email, Map<String, Obje
       // Validate email domain against allowed registration domains
       Set<String> allowedDomains = authorizerConfiguration.getAllowedEmailRegistrationDomains();
       if (allowedDomains != null
+          && !allowedDomains.isEmpty()
           && !allowedDomains.contains("all")
           && !allowedDomains.contains(domain)) {
         LOG.warn(