crm_core-8.x-3.x-dev/modules/crm_core_activity/crm_core_activity.plugin_type.yml

activity_type_plugin:
  label: 'Activity type'
  description: 'Plugin for the activity type.'
  plugin_definition_decorator_class: \Drupal\plugin\PluginDefinition\ArrayPluginDefinitionDecorator
  plugin_manager_service_id: plugin.manager.crm_core_activity.activity_type