providers/ldap: set password_change_date in check_pwd_last_set to avoid loop ending user sessions

[tograss]

Details

closes #11436
Explanation:
In (ms_)check_pwd_last_set the line
if created or pwd_last_set > user.password_change_date:
test if the pw in the ldap store is newer than the authentik one. If so
user.set_unusable_password() user.save()
Is executed. Changing the user password (correctly) ends all user sessions. See https://docs.djangoproject.com/en/5.1/topics/auth/default/#:~:text=Django%20also%20provides%20views%20and,log%20out%20all%20their%20sessions.
However, since user.password_change_date is not set the next ldap_sync will lockout the user again.
I think this wasn't a problem when during login the user pw was always saved to the authentik database. Since this changed a while ago this is now a bug.

The fix is to simply set the password_change_date to the ldap date. One might argue it should be the time the ldap sync run, but I think it is easier to understand for an administrator if the ldap date and the authentik date are the same.

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Checklist

• Local tests pass (ak test authentik/)
• The code has been formatted (make lint-fix)

If an API change has been made

• The API schema has been updated (make gen-build)

If changes to the frontend have been made

• The code has been formatted (make web)

If applicable

• The documentation has been updated
• The documentation has been formatted (make website)

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[codecov]

Codecov Report

All modified and coverable lines are covered by tests ✅

Project coverage is 92.49%. Comparing base (0f8d497) to head (701f85d).
Report is 31 commits behind head on main.

Additional details and impacted files

@@            Coverage Diff             @@
##             main   #11913      +/-   ##
==========================================
- Coverage   92.57%   92.49%   -0.09%     
==========================================
  Files         761      761              
  Lines       37813    37821       +8     
==========================================
- Hits        35004    34981      -23     
- Misses       2809     2840      +31     

Flag	Coverage Δ
e2e	48.80% <84.61%> (-0.31%)	⬇️
integration	24.93% <38.46%> (+0.01%)	⬆️
unit	90.17% <73.07%> (+0.01%)	⬆️

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