refactor: use x-tinyauth-location header and remove dupe auth modules in tinyauth auth request

[steveiliop56]

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• I have read the contributing guideline and understand that I have made the correct modifications

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Description:

Tinyauth introduced a new X-Tinyauth-Location header in the v5.0.7 version. This header allows Tinyauth to inform the reverse proxy of the location it wants the user to redirect to, avoiding the need for the custom Tinyauth login page location. It also allows for the proxy to redirect to Tinyauth's own pages for unauthorized users instead of presenting them the generic 403 error of Nginx.

Additionally, Tinyauth v5.2.0 introduced a security check to prevent the use of both the forward_auth (X-Forwarded-Host, X-Forwarded-URI) and auth_request (X-Original-URL) headers that prevents the current setup from working. This pull request, disables the forward_auth headers for the Tinyauth locations.

Benefits of this PR and context:

See above.

How Has This Been Tested?

This change will impact any users who update to this newer configuration while being on an version prior to v5.2.0. This exact patch was tested with Tinyauth's users and confirmed working as expected. Exact setups unknown.

If I understand correctly, it's the user's responsibility to review proxy configurations and apply them. However if you would like to avoid any potential confusion/potential breakage of any existing setups, I recommend at least adding a login_for=app parameter in the Tinyauth login location. This additional parameter informs the Tinyauth of the scope of the login request and helps increase security. Tinyauth can work without this parameter.

As for the proxy authentication headers, it's mandatory that part of this PR that addresses them gets merged else users with the current config will start getting 500 errors the moment they update Tinyauth to v5.2.0.

Source / References:

Release adding the header: https://github.com/tinyauthapp/tinyauth/releases/tag/v5.0.7
Release adding the new security check: https://github.com/tinyauthapp/tinyauth/releases/tag/v5.2.0
Documentation on Nginx Proxy Manager with this header: https://tinyauth.app/docs/guides/nginx-proxy-manager

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[steveiliop56]

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