custom u8string formatter for fmt library

src/common/logging/formatter.h

@@ -19,3 +19,27 @@ struct fmt::formatter<T, std::enable_if_t<std::is_enum_v<T>, char>>
     }
 };
 #endif
+
+namespace fmt {
+template <typename T = std::string_view>
+struct UTF {
+    T data;
+
+    explicit UTF(const std::u8string_view view) {
+        data = T{(const char*)&view.front(), (const char*)&view.back()};
+    }
+
+    explicit UTF(const std::u8string& str)
+        : UTF(std::u8string_view{str}) {
+    }
+};
+}
+
+template <>
+struct fmt::formatter<fmt::UTF<std::string_view>, char>
+    : formatter<std::string_view> {
+    template <typename FormatContext>
+    auto format(const UTF<std::string_view>& wrapper, FormatContext& ctx) const {
+        return formatter<std::string_view>::format(wrapper.data, ctx);
+    }
+};