Using our custom field type as a base field
At the beginning of this chapter, I stressed the importance of understanding the makeup of a field (type, widget, and formatter) so as to easily define base fields on custom entity types. This understanding allows you to navigate through Drupal core code, discover their settings, and use them on base fields. So, let's cement this understanding by seeing how our new field could be defined as a base field on a custom entity type.
Here is an example where we actually use all the available settings we defined for each of the three plugins. Note that any settings that are left out default to the values we specified in the relevant defaults method, as follows:
$fields['plate'] = BaseFieldDefinition::create('license_plate')
->setLabel(t('License plate'))
->setDescription(t('Please provide your license plate number.'))
->setSettings([
...