code: function sn_api_user_registerUrlHelperFunction(name, func) {
      if (typeof func !== "function") {
        return;
      }
      if (sn_api_user_urlHelperFunctions === undefined) {
        sn_api_user_urlHelperFunctions = [];
      }
      name = name.replace(/[^0-9a-zA-Z_]/, "");
      sn_api_user_urlHelperFunctions.push({
        name: name,
        func: func
      });
    }
docs: Register a custom function to generate URLs with {@link sn.api.user.userUrlHelper}.
  
  @param {String} name The name to give the custom function. By convention the function
  names should end with 'URL'.
  @param {Function} func The function to add to sn.api.user.userUrlHelper instances.
  @preserve