Error message needs to be more specific when user attempts to add a duplicate person

When the user attempts to add a duplicate person to the contacts, an error message with the text "This person already exists in the address book" is shown. However, it is not stated in the error message nor in the User Guide what constitutes as a duplicate person. Some users may think that duplicate people are people with the same name, but this is not the case in here. Thus, there needs to be some sort of explanation as to what counts as a duplicate contact, else there is inconvenience for users who are confused as to why they cannot add a contact, even why they specify a different value for email address.

JunWei3112 / pe

Error message needs to be more specific when user attempts to add a duplicate person #3