add
Adds a String to a custom attribute string array, or creates that array if one doesn't exist. The key and value parameters are limited to 255 characters in length. Keys and values which are too long will be truncated. Keys can only contain alphanumeric characters and underscores. Keys may not be a reserved key. See CustomAttributeValidationUtils.isValidCustomAttributeKey
Return
whether or not the custom user attribute array update was successfully logged
Parameters
key
The identifier of the custom attribute array
value
The String value of the custom attribute to be added to the array