code: function(tokenService, domainPrefix) {
    var tokenUrl = tokenService.replace(/\{DOMAIN_PREFIX\}/, domainPrefix);
    log.debug('token Url: '+ tokenUrl);
    return tokenUrl;
  }
docs: If tokenService already has a domainPrefix set because the API consumer passed in a full URL
  instead of a substitutable one ... then the replace acts as a no-op.
  
  @param tokenService
  @param domain_prefix
  @returns {*|XML|string|void}