Switch intro example to blobstore client
diff --git a/demo/include/blobstore.h b/demo/include/blobstore.h
new file mode 100644
index 0000000..d89583a
--- /dev/null
+++ b/demo/include/blobstore.h
@@ -0,0 +1,26 @@
+#pragma once
+#include "rust/cxx.h"
+#include <memory>
+
+namespace org {
+namespace blobstore {
+
+struct MultiBuf;
+struct BlobMetadata;
+
+class BlobstoreClient {
+public:
+  BlobstoreClient();
+  uint64_t put(MultiBuf &buf) const;
+  void tag(uint64_t blobid, rust::Str tag) const;
+  BlobMetadata metadata(uint64_t blobid) const;
+
+private:
+  class impl;
+  std::shared_ptr<impl> impl;
+};
+
+std::unique_ptr<BlobstoreClient> new_blobstore_client();
+
+} // namespace blobstore
+} // namespace org