[function] Email should be connected to one person even if it's written via capital letters

[emanuelkrzyszton]

Add a function that converts written email to the capital or lower letters and test if the user is assigned to the same email when he writes down the email with capital or lower letters.

[davidgmorais]

Issue fixed in 5a76a431b33d2ee1d8700e04ebebea99769d96c6