What would be the best way from your point of view to add additional validations for custom fields to the booking form to stay aligned with your plugin updates? adding custom javascript? any available hooks? Examples:

1. if custom field 1 is filled, custom field2 will be required (add error msg)
2. Depending on the service selection, custom fields should be displayed/hidden/required
3. depending on the input of custom field1, input of custom field2 must be validated against a list of criteria

Thanks for your advice! Isa