Drupal 8: Skip updating some entity fields during migration

migrate.yml

destination:
  plugin: entity:user
  # If the destination is going to update an existing user, you can optionally
  # specify the properties that should be overwritten. For example, if the
  # migration tries to import user 31 and user 31 already exists in the
  # destination database, only the 'name' and 'mail' properties of the user
  # will be overwritten. If user 31 doesn't exist, it will be created and
  # the overwrite_properties list will be ignored.
  overwrite_properties:
    - name
    - mail