fix: Add direct parameter to flow auth v2

[juliushaertl]

In SSO environments with environment variable like kerberos we may not have this authentication type on iOS devices. The current approach to still allow login is to use a direct login with configuring a rewrite on the webserver level:

RewriteEngine on
RewriteCond %{QUERY_STRING} !(?:^|&)direct=[^&]+ [NC]
#RewriteCond %{HTTP_USER_AGENT} (.*)Nextcloud\ iOS(.*)
RewriteCond %{REQUEST_METHOD} =GET
RewriteRule ^/index\.php/login/v2/flow/(.*)$ $0?%{QUERY_STRING}&direct=1 [L,QSA,NC,R=302]

• Resolves: #

Summary

• Manually tested using curl and user_saml auth with environment variable
• Testing with iOS and user_saml auth with environment variable

Checklist

• Code is properly formatted
• Sign-off message is added to all commits
• Tests (unit, integration, api and/or acceptance) are included
• Screenshots before/after for front-end changes
• Documentation (manuals or wiki) has been updated or is not required
• Backports requested where applicable (ex: critical bugfixes)

[juliushaertl]

/backport to stable29

[juliushaertl]

/backport to stable28