Fix bug 2

Author: SOHELAHMED7

src/lib/ValidationRulesBuilder.php

@@ -10,6 +10,7 @@
 use cebe\yii2openapi\lib\items\Attribute;
 use cebe\yii2openapi\lib\items\DbModel;
 use cebe\yii2openapi\lib\items\ValidationRule;
+use yii\helpers\Inflector;
 use function count;
 use function implode;
 use function in_array;
@@ -161,7 +162,7 @@ private function addExistRules(array $relations):void
                 $this->addStringRule($attribute);
             }
 
-            $targetRelation = AttributeResolver::relationName($attribute->propertyName, $attribute->fkColName);
+            $targetRelation = AttributeResolver::relationName(Inflector::variablize($attribute->camelName()), $attribute->fkColName);
             $this->rules[$attribute->columnName . '_exist'] = new ValidationRule(
                 [$attribute->columnName],
                 'exist',