I have a Firestore function where

admin
  .firestore()
  .collection('users')
  .doc(context.params.userId)
  .set({field1: false});

The problem is, this replaces the given user object with {field1: false}. I want to be able to add {field1: false} to the object while preserving all other existing fields, and also to be able to remove the field1 field from the object if it already exists.

How should I approach this?