Plan picked path callbacks in app core

src/app_core/document_platform_io.h

@@ -0,0 +1,19 @@
+#pragma once
+
+#include <string_view>
+
+namespace pp::app {
+
+enum class PickedPathAction {
+    ignore_empty_path,
+    invoke_callback,
+};
+
+[[nodiscard]] constexpr PickedPathAction plan_picked_path(std::string_view path) noexcept
+{
+    return path.empty()
+        ? PickedPathAction::ignore_empty_path
+        : PickedPathAction::invoke_callback;
+}
+
+}