Upsert User
The purpose of this is to use normalized events to create or update users in the team.users table.
This "upsert" is actually a bit different than the normal definition. Each field is indepepndently updated iff the incoming change won't make the field null. This lets us construct users that are the superset of user data from various sources
This package expects PG env variables to be defined. See index.js for what needs to be set.