Move json util code to common

So that it can be shared by CE CDM extraction tool later.

Test: m wv_factory_extraction_tool
Bug: 414642286
Change-Id: I6dba70227ce2789dd3686ebbf6ed3a0dbf68dc00

libwvdrmengine/tools/factory_upload_tool/common/include/json_utils.h

@@ -0,0 +1,19 @@
+// Copyright 2025 Google LLC. All Rights Reserved. This file and proprietary
+// source code may only be used and distributed under the Widevine License
+// Agreement.
+
+#ifndef WIDEVINE_JSON_UTILS_H_
+#define WIDEVINE_JSON_UTILS_H_
+
+#include <map>
+#include <string>
+
+namespace widevine {
+
+std::string EscapeJson(const std::string& input);
+std::string StringMapToJson(
+    const std::map<std::string, std::string>& string_map);
+
+}  // namespace widevine
+
+#endif  // WIDEVINE_JSON_UTILS_H_