Enqueue built the PostHog $groups map from hardcoded tenant and organization
context keys, so there was no way to attribute an event to any other grouping.
Adds AccountIDKey alongside them, mirroring the existing organization plumbing.

An account groups the users, organizations and tenants of one customer. Unlike
a tenant or token it is not an actor, so DistinctID is deliberately untouched —
an account-only context still yields no distinct id.

This is a new context key rather than an interface method, so NoOpAnalytics and
existing test doubles are unaffected.


Claude-Session: https://claude.ai/code/session_01CPSz1UG6ZogwBVm5NoJbja

Co-authored-by: Claude Fable 5 <noreply@anthropic.com>