Redirect after login for SSO

[bastianjoel]

Current behavior
When logging in via SSO the user is redirected to the organization dashboard even if they tried to access another page.
This is a follow up to #5763 (#5862).

Wanted behavior
The user should be redirected to the page they initially intended to access.

[bastianjoel]

To implement this we would have to pass a RelayState to the idp request.
https://github.com/bastianjoel/openslides-client/tree/sso-relay-state

For this we would have to update the samlify library in auth service which we currently do not want to do because there are signs that the library is recklessly maintained by AI. Also it introduced non documented breaking changes with the last minor version. Therefore at least a brief review of that library is needed to check what is broken and if there are any new obvious issues.
See OpenSlides/openslides-auth-service#999