add filters, update api, update api docs

backend/modules/questionnaire/views/question/_search_by_questionnaire.php

@@ -0,0 +1,35 @@
+<?php
+
+use backend\modules\questionnaire\models\Questionnaire;
+use kartik\select2\Select2;
+use yii\helpers\Html;
+use yii\widgets\ActiveForm;
+
+/* @var $this yii\web\View */
+/* @var $model backend\modules\questionnaire\models\QuestionSearch */
+/* @var $form yii\widgets\ActiveForm */
+?>
+
+<div class="question-search">
+
+    <?php $form = ActiveForm::begin([
+        'action' => ['index'],
+        'method' => 'get',
+    ]); ?>
+
+    <?= $form->field($model, 'questionnaire_id')->widget(Select2::className(),[
+        'data' => Questionnaire::find()->select(['title', 'id'])->indexBy('id')->column(),
+        'options' => ['placeholder' => 'Выберите анкету'],
+        'pluginOptions' => [
+            'allowClear' => true
+        ],
+    ])->label('Анкета') ?>
+
+
+    <div class="form-group">
+        <?= Html::submitButton('Поиск', ['class' => 'btn btn-primary']) ?>
+    </div>
+
+    <?php ActiveForm::end(); ?>
+
+</div>