Add a comment field to each time slot (D8)

I just updated one of our Drupal 8 sites to office_hours-8.x-1.0-alpha1 and ran the database updates. office_hours_update_8003() did not properly extend the schema of my office hours fields.

This site has four fields with office_hours type:

1. field_winter_hours
2. field_spring_hours
3. field_summer_hours
4. field_fall_hours

Update 8003 specifically looks for tables matching %office_hours% and adds a field field_office_hours_comment to any found. This would presumably find the node__field_office_hours and node_revision__field_office_hours tables for a field named office_hours but does not work in this case.

Those table names don't match the field names above, and the schema field names should be field_winter_hours_comment, etc, as well.

The corresponding D7 update from #2553935: Add a comment field to each time slot (D7) uses a different process to identify and update tables, and does not appear to have this problem.

I don't have time to work up a proper patch right now, but I think the replacement update could do something like this to find the tables and field names that need updating:

  $fields = \Drupal::entityManager()->getFieldMapByFieldType("office_hours");
  foreach ($fields as $entity_type => $entity_fields) {
    foreach (array_keys[$entity_fields] as $field) {
      // use $entity_type and $field to identify tables for updating.
      // add a database column called $field . "_comment"
    }
  }