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/opencc/openccxx.cpp

@@ -0,0 +1,80 @@
+#include "openccxx.h"
+#include "opencc.h"
+#include "utils.h"
+
+#include <iostream>
+#include <string>
+
+OpenCC::OpenCC(const std::string &home_dir) : od((opencc_t)-1) {
+    config_file = mstrcpy(OPENCC_DEFAULT_CONFIG_TRAD_TO_SIMP);
+    open(config_file, home_dir.c_str());
+}
+
+OpenCC::~OpenCC() {
+    if (od != (opencc_t)-1)
+        opencc_close(od);
+    free(config_file);
+}
+
+int OpenCC::open(const char *config_file, const char *home_dir) {
+    if (od != (opencc_t)-1)
+        opencc_close(od);
+    od = opencc_open(config_file, home_dir);
+    return (od == (opencc_t)-1) ? (-1) : (0);
+}
+
+long OpenCC::convert(const std::string &in, std::string &out, long length) {
+    if (od == (opencc_t)-1)
+        return -1;
+
+    if (length == -1)
+        length = in.length();
+
+    char *outbuf = opencc_convert_utf8(od, in.c_str(), length);
+
+    if (outbuf == (char *)-1)
+        return -1;
+
+    out = outbuf;
+    free(outbuf);
+
+    return length;
+}
+
+/**
+ * Warning:
+ * This method can be used only if wchar_t is encoded in UCS4 on your platform.
+ */
+long OpenCC::convert(const std::wstring &in, std::wstring &out, long length) {
+    if (od == (opencc_t)-1)
+        return -1;
+
+    size_t inbuf_left = in.length();
+    if (length >= 0 && length < (long)inbuf_left)
+        inbuf_left = length;
+
+    const ucs4_t *inbuf = (const ucs4_t *)in.c_str();
+    long count = 0;
+
+    while (inbuf_left != 0) {
+        size_t retval;
+        size_t outbuf_left;
+        ucs4_t *outbuf;
+
+        /* occupy space */
+        outbuf_left = inbuf_left + 64;
+        out.resize(count + outbuf_left);
+        outbuf = (ucs4_t *)out.c_str() + count;
+
+        retval = opencc_convert(od, (ucs4_t **)&inbuf, &inbuf_left, &outbuf, &outbuf_left);
+        if (retval == (size_t)-1)
+            return -1;
+        count += retval;
+    }
+
+    /* set the zero termination and shrink the size */
+    out.resize(count + 1);
+    out[count] = L'\0';
+
+    return count;
+}