Ensure email is case-insensitive

[mdaoustUdeS]

Problem

The email field used in Log in and Sign up (maybe somewhere else?) is case sensitive.

Email address should be treated in a case-insensitive manner.

Step to reproduce

1. Access a Flaggr instance. (e.g.: https://jdis-ia.dinf.usherbrooke.ca/1/)
2. Sign up a new user with mixed case email address. (e.g. Demo@Test.com)
3. Log in with the same credential, but with different case in email. (e.g. dEmo@tEst.com)

Access should be granted.

Warning

The password field MUST stay case sensitive.

Reference

https://stackoverflow.com/a/9808332