Trigger table update when changes are made inside of baseFieldDefinitions

Question

I have a entity that has allready been enabled and the baseFieldDefinitions have created the fields in the database. But now i want to add a single field, and the obvious solution in dev is just to uninstall --> reinstall. But if the site is in production there must be a way to run a retrigger of that method? I have tried to clear the cache and updateing via the update.php file, but to no prevail. Ive allso tried to just create a entity with the new field in it, to see if it behaved like a ordinary ORM system where the initial creation of a entity has update triggers tied to it, but that allso did not work.

So im at a lost, i read through the drupal entity api, and a guy asked the exact same question but with no answer, so im thinking that it would be nice to put the answer here whatever it might be :)

My entity declaration(with the new field "processed" added):

 @ContentEntityType(
 *   id = "person",
 *   label = @Translation("A entity to contain contact information for future customers"),
 *   handlers = {
 *     "view_builder" = "Drupal\Core\Entity\EntityViewBuilder",
 *     "list_builder" = "Drupal\person\PersonListBuilder",
 *     "views_data" = "Drupal\person\Entity\PersonViewsData",
 *     "form" = {
 *       "default" = "Drupal\person\Form\PersonForm",
 *       "add" = "Drupal\person\Form\PersonForm",
 *       "edit" = "Drupal\person\Form\PersonForm",
 *       "delete" = "Drupal\person\Form\PersonDeleteForm",
 *     },
 *     "access" = "Drupal\person\PersonAccessControlHandler",
 *   },
 *   base_table = "person",
 *   admin_permission = "administer Person entities",
 *   entity_keys = {
 *     "id" = "id",
 *     "label" = "name",
 *     "uuid" = "uuid",
 *     "uid" = "user_id",
 *     "email" = "email",
 *     "phone" = "phone",
 *     "description" = "description",
 *     "langcode" = "langcode",
 *     "processed" = "processed"
 *   },
 *   links = {
 *     "canonical" = "/admin/person/{person}",
 *     "edit-form" = "/admin/person/{person}/edit",
 *     "delete-form" = "/admin/person/{person}/delete"
 *   },
 *   field_ui_base_route = "person.settings"
 * )
 */
class Person extends ContentEntityBase implements PersonInterface
{

My baseFieldDefinitions method inside the entity looks like this:

 /**
     * {@inheritdoc}
     */
    public static function baseFieldDefinitions(EntityTypeInterface $entity_type)
    {
        $fields['id'] = BaseFieldDefinition::create('integer')
            ->setLabel(t('ID'))
            ->setDescription(t('The ID of the A entity to contain contact information for future customers entity.'))
            ->setReadOnly(TRUE);
        $fields['uuid'] = BaseFieldDefinition::create('uuid')
            ->setLabel(t('UUID'))
            ->setDescription(t('The UUID of the A entity to contain contact information for future customers entity.'))
            ->setReadOnly(TRUE);

        $fields['user_id'] = BaseFieldDefinition::create('entity_reference')
            ->setLabel(t('Authored by'))
            ->setDescription(t('The user ID of author of the A entity to contain contact information for future customers entity.'))
            ->setRevisionable(TRUE)
            ->setSetting('target_type', 'user')
            ->setSetting('handler', 'default')
            ->setDefaultValueCallback('Drupal\node\Entity\Node::getCurrentUserId')
            ->setTranslatable(TRUE)
            ->setDisplayOptions('view', array(
                'label' => 'hidden',
                'type' => 'author',
                'weight' => 0,
            ))
            ->setDisplayOptions('form', array(
                'type' => 'entity_reference_autocomplete',
                'weight' => 5,
                'settings' => array(
                    'match_operator' => 'CONTAINS',
                    'size' => '60',
                    'autocomplete_type' => 'tags',
                    'placeholder' => '',
                ),
            ))
            ->setDisplayConfigurable('form', TRUE)
            ->setDisplayConfigurable('view', TRUE);

        $fields['name'] = BaseFieldDefinition::create('string')
            ->setLabel(t('Name'))
            ->setDescription(t('The name of the A entity to contain contact information for future customers entity.'))
            ->setSettings(array(
                'max_length' => 50,
                'text_processing' => 0,
            ))
            ->setDefaultValue('')
            ->setDisplayOptions('view', array(
                'label' => 'above',
                'type' => 'string',
                'weight' => -4,
            ))
            ->setDisplayOptions('form', array(
                'type' => 'string_textfield',
                'weight' => -4,
            ))
            ->setDisplayConfigurable('form', TRUE)
            ->setDisplayConfigurable('view', TRUE);

        $fields['status'] = BaseFieldDefinition::create('boolean')
            ->setLabel(t('Publishing status'))
            ->setDescription(t('A boolean indicating whether the A entity to contain contact information for future customers is published.'))
            ->setDefaultValue(TRUE);

        $fields['processed'] = BaseFieldDefinition::create('boolean')
            ->setLabel(t('Processed'))
            ->setDescription(t('A boolean describeing if a customer has been contacted or not.'))
            ->setDefaultValue(FALSE);

        $fields['langcode'] = BaseFieldDefinition::create('language')
            ->setLabel(t('Language code'))
            ->setDescription(t('The language code for the A entity to contain contact information for future customers entity.'));

        $fields['created'] = BaseFieldDefinition::create('created')
            ->setLabel(t('Created'))
            ->setDescription(t('The time that the entity was created.'));

        $fields['changed'] = BaseFieldDefinition::create('changed')
            ->setLabel(t('Changed'))
            ->setDescription(t('The time that the entity was last edited.'));

        $fields['phone'] = BaseFieldDefinition::create('string')
            ->setLabel(t('Phone'))
            ->setDescription(t('The phonenumber of future customers'))
            ->setDefaultValue('');

        $fields['email'] = BaseFieldDefinition::create('string')
            ->setLabel(t('Email'))
            ->setDescription(t('The email of future customers'))
            ->setDefaultValue('');

        $fields['description'] = BaseFieldDefinition::create('string')
            ->setLabel(t('Description'))
            ->setDescription(t('A description of whatever task the future customer wants to be contacted about'))
            ->setDefaultValue('');
        return $fields;
    }

Answer 1

See node_update_8001():

/**
 * Add 'revision_translation_affected' field to 'node' entities.
 */
function node_update_8001() {
  // Install the definition that this field had in
  // \Drupal\node\Entity\Node::baseFieldDefinitions()
  // at the time that this update function was written. If/when code is
  // deployed that changes that definition, the corresponding module must
  // implement an update function that invokes
  // \Drupal::entityDefinitionUpdateManager()->updateFieldStorageDefinition()
  // with the new definition.
  $storage_definition = BaseFieldDefinition::create('boolean')
      ->setLabel(t('Revision translation affected'))
      ->setDescription(t('Indicates if the last edit of a translation belongs to current revision.'))
      ->setReadOnly(TRUE)
      ->setRevisionable(TRUE)
      ->setTranslatable(TRUE);

  \Drupal::entityDefinitionUpdateManager()
    ->installFieldStorageDefinition('revision_translation_affected', 'node', 'node', $storage_definition);
}