Summary:
* Remove adjustSession hack, interfering with loading docs under saml.
* Allow the anonymous user to receive an empty list of workspaces for
the merged org.
* Behave better on first page load when org is in path - this used to
fail because of lack of cookie. This is very visible in grist-core,
as a failure to load localhost:8484 on first visit.
* Mark cookie explicitly as SameSite=Lax to remove a warning in firefox.
* Make errorPages available in grist-core.
This changes the default behavior of grist-core to now start off in
anonymous mode, with an explicit sign-in step available. If SAML is not configured,
the sign-in operation will unconditionally sign the user in as a default
user, without any password check or other security. The user email is
taken from GRIST_DEFAULT_EMAIL if set. This is a significant change, but
makes anonymous mode available in grist-core (which is convenient
for testing) and makes behavior with and without SAML much more consistent.
Test Plan: updated test; manual (time to start adding grist-core tests though!)
Reviewers: dsagal
Reviewed By: dsagal
Differential Revision: https://phab.getgrist.com/D2980
