[C2] Improvements to 2FA

[ywarnier]

• The 2FA authentication should send the name of the site (as in the "E-learning portal name" setting in Chamilo, because currently we only send the e-mail address and that doesn't allow someone to remember what service it was for. It should be something like 'Test portal: y@myemail.com' instead of just 'y@myemail.com'.
• When you setup 2FA, you normally have to confirm the 2FA activation by entering directly the code you get in your 2FA application. You scan the QR code and immediately give the code that appears, and then your 2FA is enabled.
• When I login and if the code was wrong, I expect a message telling me so, and in my tests I just get a login form refresh but nothing tells me what was wrong.
• To disable 2FA or change your password, you have to enter your 2FA code (not just to login).

Originally posted by @ywarnier in #5836 (comment)

[christianbeeznest]

The improvements are added in this PR #6217

Thanks for confirmation

[ywarnier]

More improvements needed:

• When I enable 2FA and enter the 2FA code to validate, I get back to my profile (all good). But when I return to "Change Password", the 2FA checkbox is still checked (all good) and because of that the QR code still appears. If I already have something in my mfa_secret field, the QR code should not appear anymore (because otherwise users might get confused and think it didn't work and they have to scan it again)
• When I enable 2FA and I log out, when I try to login again, it just reloads the login form (and it doesn't ask me for my 2FA code). That was working previously.