SSR SPA do not work upon preview link click in the channels overview

Path to reproduce:
1) switch to list view in the CM;
2) click `preview` link for an SSR SPA.

Actual:
SPA gives 500.

Expected:
SPA works normally.

Issue:
SPA detects the preview mode and tries to fetch a page model via preview URL but it fails because there is no JSESSIONID cookie under `/site`.

Solution:
Perform SSO handshake before opening the link.