Login redirects for SSO flow do not include the original page's query string

Summary

When using SSO, attempting to access a GitLab URL with a query string (e.g. a pre-filled merge request creation URL from the output of git push) while logged out redirects to the URL without the query string, breaking functionality for operations which rely on the query string.

This causes confusion and frustration for our users. It looks like the fix for the previous version of this issue (original URL missed entirely) did not account for query strings.

Steps to reproduce

• User is logged out
• User opens an SSO-protected GitLab URL with a query string

Current behavior

• User is redirected to login flow
• User logs in
• User is redirected to original URL, without original query string

Expected behavior

• User is redirected to login flow
• User logs in
• User is redirected to original URL, with original query string