Added validation to variable validation rules to validate that the validation rules are valid

closes #988

app/Traits/Services/ValidatesValidationRules.php

@@ -0,0 +1,40 @@
+<?php
+
+namespace Pterodactyl\Traits\Services;
+
+use BadMethodCallException;
+use Illuminate\Support\Str;
+use Illuminate\Contracts\Validation\Factory;
+use Pterodactyl\Exceptions\Service\Egg\Variable\BadValidationRuleException;
+
+trait ValidatesValidationRules
+{
+    /**
+     * @return \Illuminate\Contracts\Validation\Factory
+     */
+    abstract protected function getValidator(): Factory;
+
+    /**
+     * Validate that the rules being provided are valid for Laravel and can
+     * be resolved.
+     *
+     * @param array|string $rules
+     *
+     * @throws \Pterodactyl\Exceptions\Service\Egg\Variable\BadValidationRuleException
+     */
+    public function validateRules($rules)
+    {
+        try {
+            $this->getValidator()->make(['__TEST' => 'test'], ['__TEST' => $rules])->fails();
+        } catch (BadMethodCallException $exception) {
+            $matches = [];
+            if (preg_match('/Method \[(.+)\] does not exist\./', $exception->getMessage(), $matches)) {
+                throw new BadValidationRuleException(trans('exceptions.nest.variables.bad_validation_rule', [
+                    'rule' => Str::snake(str_replace('validate', '', array_get($matches, 1, 'unknownRule'))),
+                ]), $exception);
+            }
+
+            throw $exception;
+        }
+    }
+}