The list of fields to extract from the
Request object and use when querying the database.
This can either be a simple array of field names, or a set of key/value pairs, which map
the field names in the request to database field names.
For example, if you had a form field name
username, which mapped to a database field named
username, you could use the following in the
This is especially relevant for document databases, where you may want to map a form field to a nested document field: ``` 'fields' => ['username' => 'login.username', 'password'], ```
protected $_fields = ;