fix: APIHelper에서 tryCache가 잘못된 타입 지정인 버그

src/sammo/APICacheResult.php

@@ -0,0 +1,12 @@
+<?php
+namespace sammo;
+
+class APICacheResult{
+    function __construct(
+        public ?\DateTimeInterface $lastModified,
+        public ?string $etag,
+    )
+    {
+
+    }
+}

src/sammo/APIHelper.php

@@ -82,8 +82,8 @@ class APIHelper
 
             $cacheResult = $obj->tryCache();
             if ($cacheResult !== null) {
-                /** @var \DateTimeInterface $lastModified  */
-                [$lastModified, $etag] = $cacheResult;
+                $lastModified = $cacheResult->lastModified;
+                $etag = $cacheResult->etag;
 
                 if ($lastModified !== null) {
                     header("Last-Modified: " . gmdate("D, d M Y H:i:s", Util::toInt(TimeUtil::DateTimeToSeconds($lastModified, true))) . " GMT");

src/sammo/BaseAPI.php

@@ -22,7 +22,7 @@ abstract class BaseAPI
     /** @return null|string|array */
     abstract function launch(Session $session, ?\DateTimeInterface $modifiedSince, ?string $reqEtag);
 
-    public function tryCache():?string{
+    public function tryCache():?APICacheResult{
         return null;
     }
 }