Add sameSite option to sessions

[jonowu]

Adds a sameSite option to the session options for cookies. Can be one of true, false, 'strict', 'lax' or 'none' as per Mozilla docs. The option defaults to 'lax' which is in line with existing behaviour.

This option will be useful for users who have deployed their keystone instance to a different site from their frontend, e.g. hosting keystone on example.herokuapp.com with the frontend on example.vercel.app.

[changeset-bot]

🦋 Changeset detected

Latest commit: 7611881

The changes in this PR will be included in the next version bump.

This PR includes changesets to release 11 packages

Name	Type
@keystone-next/website	Minor
@keystone-next/keystone	Minor
@keystone-next/test-utils-legacy	Patch
@keystone-next/auth	Major
@keystone-next/example-auth	Patch
@keystone-next/app-basic	Patch
@keystone-next/example-ecommerce	Patch
keystone-next-app	Patch
@keystone-next/example-roles	Patch
@keystone-next/example-sandbox	Patch
@keystone-next/example-with-auth	Patch

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🔍 Inspect: https://vercel.com/keystonejs/keystone-next-docs/n7oEeBphfkrNLyFYGzTGXNWE59qB
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@keystone-next/example-sandbox	Configuration

[JedWatson]

Looks great, thanks @jonowu!

[kilinkis]

thanks for this!