feat(core): add system store service interface

Signed-off-by: Sebastian Krupinski <krupinski01@gmail.com>

shared/lib/SystemStore/BlobInfo.php

@@ -0,0 +1,40 @@
+<?php
+
+declare(strict_types=1);
+
+namespace KTXF\SystemStore;
+
+use DateTimeImmutable;
+use InvalidArgumentException;
+
+/**
+ * Provider-neutral information about a blob in a system store.
+ */
+final readonly class BlobInfo
+{
+    public function __construct(
+        public string $key,
+        public string $mimeType,
+        public int $size,
+        public string $etag,
+        public DateTimeImmutable $modifiedAt,
+        public array $attributes = [],
+    ) {
+        if ($this->key === '') {
+            throw new InvalidArgumentException('Blob key cannot be empty');
+        }
+
+        if ($this->mimeType === '') {
+            throw new InvalidArgumentException('Blob MIME type cannot be empty');
+        }
+
+        if ($this->size < 0) {
+            throw new InvalidArgumentException('Blob size cannot be negative');
+        }
+
+        if ($this->etag === '') {
+            throw new InvalidArgumentException('Blob ETag cannot be empty');
+        }
+    }
+
+}