Fix case sensitivity issue in username handling

[tdrivas]

This PR resolves an issue where Django Allauth was treating all usernames as lowercase during authentication, preventing users with capital letters in their usernames from logging in.

The problem
Usernames were correctly stored in the database with their original case (e.g., Bob), but authentication failed if users entered their names with uppercase letters.

Solution
Updated ACCOUNT_PRESERVE_USERNAME_CASING to True so to ensure usernames are not altered during authentication and are matched exactly as stored in the database.

Impact

• Users can now login using the their, exact case, username as stored in the db.
• No impact on existing stored usernames as only the authentication behavior has been adjusted.

Test new functionality (Manual tests)

• Tested logging in with usernames having uppercase letters
• Ensured that new users can sign up and log in as expected.
• Verified password reset still works with case-sensitive usernames

[duke-nyuki]

Task linked: QF-4962 Cannot login to admin if the username starts with a Capital letter

[suricactus]

I am only afraid what will be the implications of such change. Let us discuss in the next meeting.

Btw, would you mind adding the docs in settings file since you are on it?

[gounux]

Could test locally, auth with uppercases in the login username seems to work fine !

I am only afraid what will be the implications of such change

Feeling the same.

[suricactus]

@tdrivas let us know what tests you have performed to ensure no regressions are there.

[tdrivas]

@tdrivas let us know what tests you have performed to ensure no regressions are there.

Check updated description please!

[suricactus]

Test new functionality (Manual tests)
Tested logging in with usernames having uppercase letters
Ensured that new users can sign up and log in as expected.
Verified password reset still works with case-sensitive usernames

A few other manual tests on top of the ones you performed:

• ensure usernames with lowercase letters can login
• ensure that username "SURICACTUS" or similar can access their profile no matter if they are written in lowercase or uppercase in the login form for:
• a) Django admin
• b) app.qfiled.cloud login
• ensure that after login, one can load host.com/a/SURICACTUS and host.com/a/suricactus with the same result.

I believe we can write a new test function similar to

QFieldCloud/docker-app/qfieldcloud/authentication/tests/test_authentication.py

Line 63 in d092586

def test_login_logout(self):

with username with capitals.

[suricactus]

Last two bits and we are ready.

[suricactus]

I will leave this one for the next release. Not huge risk, but still sounds like an imporant settings we change.