def check_availability(identifier, custom_headers:nil)
      response = check_availability_async(identifier, custom_headers:custom_headers).value!
      response.body unless response.nil?
    end
def check_availability(identifier, custom_headers:nil)
      response = check_availability_async(identifier, custom_headers:custom_headers).value!
      response.body unless response.nil?
    end
Check if a domain is available for registration.

 Check if a domain is available for registration.

 @param identifier [NameIdentifier] Name of the domain.
 @param custom_headers [Hash{String => String}] A hash of custom headers that
 will be added to the HTTP request.

 @return [DomainAvailablilityCheckResult] operation results.