How other modules associate with the User entity?

Support
#1

For new composite project (Jmix 2.0 flow UI)

  1. create new composite project: test0707

  2. create sub-project (Full-Stack Application) : main

  • Built-in User entity
  1. create sub-project (Add-On) : org
  • create entiry: Emp

Q: How does Emp associate with the User entity?