Set the cookie SameSite directive to Strict

[sandbergja]

Success criteria

• DSS's Set-Cookie response header includes "SameSite=Strict"
• Confirm that authentication works correctly when one follows a Login via CAS option on a study with protected file content hosted on the DSS server. Ex: https://dss.princeton.edu/studies/2

Rationale

This reduces the number of scenarios in which the cookie will be sent, providing better CSRF protection and reducing the size of the Cookies header in some cases. Part of pulibrary/dacs_handbook#154

Example PR

pulibrary/orangelight#3932

Tradeoff

If a user logs into DSS, navigates to a non-Princeton Web site (e.g. Outlook), and then clicks a link from that Web site back to DSS, they will need to log in to DSS again.

Further reading

I found this from Mozilla, this from Portswigger, and this blog post from Andrew Lock to be helpful in understanding this topic.