Disable user profiles on login screen

[frenck]

Proposed change

This PR disables the ability to log in using the user profile on the login page.

More details with reasoning behind this will be published separately from this PR in a blog post.

Before & after screenshot:

ℹ️ This PR focusses on the minimal change set to make this happen while making the linters and tests happy.

Type of change

• Dependency upgrade
• Bugfix (non-breaking change which fixes an issue)
• New integration (thank you!)
• New feature (which adds functionality to an existing integration)
• Deprecation (breaking change to happen in the future)
• Breaking change (fix/feature causing existing functionality to break)
• Code quality improvements to existing code or addition of tests

Additional information

• This PR fixes or closes issue: fixes #
• This PR is related to issue:
• Link to documentation pull request:

Checklist

• The code change is tested and works locally.
• Local tests pass. Your PR cannot be merged unless tests pass
• There is no commented out code in this PR.
• I have followed the development checklist
• I have followed the perfect PR recommendations
• The code has been formatted using Ruff (ruff format homeassistant tests)
• Tests have been added to verify that the new code works.

If user exposed functionality or configuration variables are added/changed:

• Documentation added/updated for www.home-assistant.io

If the code communicates with devices, web services, or third-party tools:

• The manifest file has all fields filled out correctly.
  Updated and included derived files by running: python3 -m script.hassfest.
• New or updated dependencies have been added to requirements_all.txt.
  Updated by running python3 -m script.gen_requirements_all.
• For the updated dependencies - a link to the changelog, or at minimum a diff between library versions is added to the PR description.
• Untested files have been added to .coveragerc.

To help with the load of incoming pull requests:

• I have reviewed two other open pull requests in this repository.

[home-assistant]

Hey there @home-assistant/core, mind taking a look at this pull request as it has been labeled with an integration (auth) you are listed as a code owner for? Thanks!

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[PattaFeuFeu]

Thanks for listening to—what I assume was the reason here—security concerns! 🙏

[jprokopowich]

Is this going to affect the mfa module and authentication related to it?

[edwinligthart]

Thanks for taking our concerns seriously.

Only point for future issues, don't treat us like we are stupid in the beginning. We all understand everyone makes misstakes and it will take some time to fix things. Just say: we are reviewing/implementing/fixing.

But anyway like they say in dutch; ""beter ten halve gekeerd dan ten hele gedwaald": "better to turn back half way than to go astray altogether"

Thanks

[PattaFeuFeu]

More details with reasoning behind this will be published separately from this PR in a blog post.

For reference: The blog post mentioned above: https://www.home-assistant.io/blog/2023/12/14/disabling-new-login-page-functionality/