RAGFlow go API server (#13240)

# RAGFlow Go Implementation Plan 🚀

This repository tracks the progress of porting RAGFlow to Go. We'll
implement core features and provide performance comparisons between
Python and Go versions.

## Implementation Checklist

- [x] User Management APIs
- [x] Dataset Management Operations
- [x] Retrieval Test
- [x] Chat Management Operations
- [x] Infinity Go SDK

---------

Signed-off-by: Jin Hai <haijin.chn@gmail.com>
Co-authored-by: Yingfeng Zhang <yingfeng.zhang@gmail.com>

internal/cpp/re2/pod_array.h

@@ -0,0 +1,55 @@
+// Copyright 2018 The RE2 Authors.  All Rights Reserved.
+// Use of this source code is governed by a BSD-style
+// license that can be found in the LICENSE file.
+
+#ifndef RE2_POD_ARRAY_H_
+#define RE2_POD_ARRAY_H_
+
+#include <memory>
+#include <type_traits>
+
+namespace re2 {
+
+template <typename T>
+class PODArray {
+ public:
+  static_assert(std::is_trivial<T>::value && std::is_standard_layout<T>::value,
+                "T must be POD");
+
+  PODArray()
+      : ptr_() {}
+  explicit PODArray(int len)
+      : ptr_(std::allocator<T>().allocate(len), Deleter(len)) {}
+
+  T* data() const {
+    return ptr_.get();
+  }
+
+  int size() const {
+    return ptr_.get_deleter().len_;
+  }
+
+  T& operator[](int pos) const {
+    return ptr_[pos];
+  }
+
+ private:
+  struct Deleter {
+    Deleter()
+        : len_(0) {}
+    explicit Deleter(int len)
+        : len_(len) {}
+
+    void operator()(T* ptr) const {
+      std::allocator<T>().deallocate(ptr, len_);
+    }
+
+    int len_;
+  };
+
+  std::unique_ptr<T[], Deleter> ptr_;
+};
+
+}  // namespace re2
+
+#endif  // RE2_POD_ARRAY_H_