Implement django-allauth

[jh-RLI]

Description of the issue

We want to implement #1363 for that we need a more sophisticated login approach that offers openid connect based user authentication. The package django-allauth offers this out of the box.

Ideas of solution

Install https://docs.allauth.org/en/latest/
Check if the new login system can be merged with the django allauth backend.

Workflow checklist

• I am aware of the workflow in CONTRIBUTING.md

[jh-RLI]

Maybe django axes need to be configured https://django-axes.readthedocs.io/en/latest/6_integration.html

[jh-RLI]

We consider to first update django to a more recent version. This PR offers the relevant changes to migrate to django 5 but it requires more testing.

#1884

[jh-RLI]

In general, it works now. The missing parts are: I

• overwrite all templates in the branch currently only login / logout in OEP style is already in it. It's just a bit of hard work :)
• Extend the SocialAdapter to read extra data and populate the user correctly .
• Review new settings, is something missing?
• Integrate with OEP CreateUserForm.

[jh-RLI]

for some reason currently the social login user´s mail is not verified but no error is raised. When someone uses a social login we can assume the mail to be verified.

I also migrated the password change form from our current approach to allauth.

[jh-RLI]

Okay after setting the verification setting to mandatory this works again. I think we set it to optional on purp. but it seems odd to have a unverified user acc. in our database that can act as a verified one.