(yiisoft#13105) Add yiiActiveForm validate_only property for skipping…

… form auto-submission

JS validation example:

form = $('#someForm');
form.data('yiiActiveForm').validate_only = true;
form.one('afterValidate', afterValidateEvent);
form.yiiActiveForm('validate', true); //run validation

function afterValidateEvent() {
    if ($('#someForm').find('.has-error').length) {
       // Validation failed
    }
     // Validation successed
}

framework/assets/yii.activeForm.js

@@ -218,6 +218,7 @@
                     attributes: attributes,
                     submitting: false,
                     validated: false,
+                    validate_only: false, // validate without auto submitting
                     options: getFormOptions($form)
                 });
 
@@ -754,12 +755,14 @@
                 data.submitting = false;
             } else {
                 data.validated = true;
-                if (data.submitObject) {
-                    applyButtonOptions($form, data.submitObject);
-                }
-                $form.submit();
-                if (data.submitObject) {
-                    restoreButtonOptions($form);
+                if (!data.validate_only) {
+                    if (data.submitObject) {
+                        applyButtonOptions($form, data.submitObject);
+                    }
+                    $form.submit();
+                    if (data.submitObject) {
+                        restoreButtonOptions($form);
+                    }
                 }
             }
         } else {