Fix bug while releasing session key:

Uncaught exception 'Meritoo\LimeSurvey\ApiClient\Exception\UnknownMethodException' with message 'The 'get_session_key' type of name of method used while talking to the LimeSurvey's API is unknown

src/Meritoo/LimeSurvey/ApiClient/Client/Client.php

@@ -77,7 +77,8 @@ class Client
     public function run($method, $arguments = [])
     {
         /*
-         * Let's validate method
+         * Let's validate method.
+         * It's called in the JsonRpcClientManager::runMethod() too, but I want to verify it before getting session key.
          */
         $method = MethodType::getValidatedMethod($method);
 

src/Meritoo/LimeSurvey/ApiClient/Type/MethodType.php

@@ -96,7 +96,7 @@ class MethodType extends BaseType
      */
     public static function getValidatedMethod($method)
     {
-        if ((new static())->isCorrectType($method)) {
+        if ((new static())->isCorrectType($method) || (new SystemMethodType())->isCorrectType($method)) {
             return $method;
         }