feat(core): add tenant system store contracts and configuration

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

shared/lib/SystemStore/SystemStoreManagerInterface.php

@@ -0,0 +1,38 @@
+<?php
+
+declare(strict_types=1);
+
+namespace KTXF\SystemStore;
+
+use KTXF\Resource\BinaryResource;
+
+/**
+ * Tenant-scoped access to logical internal stores.
+ */
+interface SystemStoreManagerInterface
+{
+    public function stat(string $tenantId, string $store, string $key): ?BlobInfo;
+
+    public function read(string $tenantId, string $store, string $key): ?BinaryResource;
+
+    public function write(
+        string $tenantId,
+        string $store,
+        string $key,
+        BinaryResource $content,
+        array $metadata = [],
+        ?WriteCondition $condition = null,
+    ): BlobInfo;
+
+    public function delete(
+        string $tenantId,
+        string $store,
+        string $key,
+        ?WriteCondition $condition = null,
+    ): bool;
+
+    /**
+     * @return iterable<BlobInfo>
+     */
+    public function list(string $tenantId, string $store, string $prefix = ''): iterable;
+}