Definition
`posthog.identify(userId, traits)` and `mixpanel.identify(userId)` mark a user as known. Every event after the identify call gets associated with that user. Most backends also merge prior anonymous activity for the same browser into the identified user.
Common bugs
Dropping the identify call leaves users anonymous, splitting one person's journey into two profiles. Calling identify with the wrong ID (a session token, for example) creates one user per session. Skene flags identify calls that disappear from the login flow.
