Fix support to use login from multiple browsers

Problem/Motivation

When activating

Enable Keycloak-initiated single sign-out

it is only possible for a user to be logged in in one broser at a time. As soon as the same user logs in using another browser (or a private tab) the first user is logged out on the next page view.

Steps to reproduce

1. Log in to the site using keycloak
2. Log in on the same site and as the same user as 1. using keycloak in another browser
3. Refresh the page on step 1.
4. Notice how you are logged out on the browser from step 1.

Proposed resolution

The module should store the keycloak session data in the ession instead of @tempstore.private since that is shared across all sessions for a specific user.