This code is executed once React DevTools panels are mounted, basically
when user opens browser's DevTools. Based on this fact, session in this
case is defined by browser's DevTools session, while they are open. A
session can involve debugging multiple React pages. `crypto.randomUUID`
is used to generate random user id.
Corresponding logger config changes -
[D50267871](https://www.internalfb.com/diff/D50267871).