Set `SESSION_COOKIE_SAMESITE=Lax` for `devstack_docker` environment by default to allow login to LMS service.
Set `SESSION_COOKIE_SAMESITE=Lax` for `devstack_docker` environment by default to allow login to LMS service.

This is a fix for `devstack_docker` default value set to `Lax` for `DCS_SESSION_COOKIE_SAMESITE`. It was defaulting to `SameSite=None` which requires a secure site which `localhost` site does not by default.

Setting this `SameSite` cookie attribute to something other than `None` will continue to allow login to the LMS for `devstack_docker` environment.

Regards to #23671 and https://discuss.openedx.org/t/lti-xblock-and-samesite/759/16
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