🔴 Fix/user authentication enforcement

[brunotho]

BEFORE REVIEW:
to do:
- fully remove password requirements for User.update

Ready for review

This PR:

• fixes the previously spotty Devise user authentication
• moves authenticate_user! to ApplicationController and exempts the public PagesController
• removes Devise validatable from User model and adds custom email validation (custom password validation was already written). This was done to remove the doubled error message a user would get when attempting to submit an invalid password.
• removes the new password / password confirmation form fields being required for any change to User
• removes current password being required for updates to User aside from password itself
• makes visual display of a field being required in sign-up form match the underlying validations
• adds a authorization guard to Users#show to permit only friends to view a users profile

#141 #147

[emmvs]

Hmm, it looks like I cannot view profiles of my friends anymore either 🤔 Could you check if it's the same for you?