Refs: HP-2491

kc_action_status is used to indicate e.g. whether a requested
password change was successful or not. It will be returned
from tunnistamo along with code and state to the callback url
the same way keycloak does it. This should make a later
transtition to keycloak (by dropping tunnistamo from the middle)
not require extra work for any logic using kc_action_status.

Upon login the kc_action_status is saved to the session from
which it is then retrieved in TunnistamoAuthorizeEndpoint.

Refs: HP-2491