fix: escape for getting string literal

Author: WZhuo

src/iceberg/expression/literal.cc

@@ -24,6 +24,8 @@
 #include <cstdint>
 #include <string>
 
+#include <nlohmann/json.hpp>
+
 #include "iceberg/util/checked_cast.h"
 #include "iceberg/util/conversions.h"
 #include "iceberg/util/macros.h"
@@ -488,7 +490,8 @@ std::string Literal::ToString() const {
           .value_or("invalid literal of type decimal");
     }
     case TypeId::kString: {
-      return "\"" + std::get<std::string>(value_) + "\"";
+      nlohmann::json json = std::get<std::string>(value_);
+      return json.dump();
     }
     case TypeId::kUuid: {
       return std::get<Uuid>(value_).ToString();

src/iceberg/test/literal_test.cc

@@ -546,9 +546,9 @@ INSTANTIATE_TEST_SUITE_P(
                               .expected_type_id = TypeId::kDecimal,
                               .expected_string = "0"},
         BasicLiteralTestParam{.test_name = "String",
-                              .literal = Literal::String("hello world"),
+                              .literal = Literal::String("hello \" world"),
                               .expected_type_id = TypeId::kString,
-                              .expected_string = "\"hello world\""},
+                              .expected_string = "\"hello \\\" world\""},
         BasicLiteralTestParam{
             .test_name = "Uuid",
             .literal = Literal::UUID(