Как работать с формами
https://p0vidl0.info/yii2-polya-activeform.html
https://webformyself.com/yii2-activeform-chast-5/
https://www.yiiframework.com/doc/guide/2.0/en/input-forms
https://stackoverflow.com/questions/37765796/how-to-layout-yii2-form-fields-side-by-side/37772138#37772138