The custom fields API endpoint can be accessed through the customFields() method. In order to limit the query
to a single custom field, the ID of the custom field must be passed as a parameter to this method.
By default, the following actions are available for custom fields:
- index()
- Returns a list of all custom fields.
- show()
- Returns a single custom field. Requires a valid custom field ID.
- create()
- Creates a new custom field.
- update()
- Updates an existing custom field.
- delete()
- Deletes an existing custom field.