feat: Store sessionId info in cookie with localstorage

[benjackwhite]

Changes

Related to PostHog/posthog#15026 but with same-root domains

Currently we only store the distinctId in the cookie when using localStorage+cookie (the default). This allows us to tie cross-domain sessions together. We don't currently have the $sesid value stored though, which means Recordings are not linked.

This updates the code to allow multiple values to be stored in the cookie, now including the special $sesid value.

NOTE: One missing thing here is good handling of multiple active domain sessions. For example if I have a session on posthog.com and then one on app.posthog.com, they will have the same session_id. But if the session times out on posthog.com but not on app.posthog.com then there will be two sessions with a race to decide which reset occurs. We could perhaps mitigate this by periodically "refreshing" from the cookie store but this feels overkill for now.

Checklist

• Tests for new code (see advice on the tests we use)
• Accounted for the impact of any changes across different browsers

[github-actions]

Size Change: +176 B (0%)

Total Size: 665 kB

Filename	Size	Change
dist/array.full.js	172 kB	+44 B (0%)
dist/array.js	114 kB	+44 B (0%)
dist/es.js	113 kB	+44 B (0%)
dist/module.js	114 kB	+44 B (0%)

ℹ️ View Unchanged

Filename	Size
dist/recorder-v2.js	93.6 kB
dist/recorder.js	58.3 kB

_{compressed-size-action}

[pauldambra]

I'd bump minor but otherwise 👍

[benjackwhite]

I'd bump minor but otherwise 👍

I was thinking - nothing about the api changes. But i guess it is a new "feature"...