Keep the colleague's microbu-esp32c5 tree in this repository

obu-firmware builds against vanetza-idf from microbu-esp32c5/external, but
that tree was gitignored, so a clone of this repository could not build the
firmware it ships. It is now committed here as ordinary files in its own
folder, microbu-esp32c5/: the colleague's commit cf4b99f plus the V2X2MAP
bridge's signature verification (--trust) used on the bench. Nothing is
fetched from or pushed to the colleague's repository; this repository and
its remotes carry everything. The folder's own .gitignore keeps build output,
downloaded components and private key material out, as it did there; the
committed file set is identical to that repository's tracked files.

The ESP32-C5 is still flashed from obu-firmware/, which only takes
vanetza-idf from microbu-esp32c5/, so the two stay separate folders.
FLASHING.md says how to take a newer version of the colleague's tree (copy
it over the folder, rebuild, test, commit).

microbu-esp32c5/external/vanetza-idf/vanetza/common/serialization.hpp

@@ -0,0 +1,83 @@
+#ifndef SERIALIZATION_HPP_U2YGHSPB
+#define SERIALIZATION_HPP_U2YGHSPB
+
+#include <vanetza/common/archives.hpp>
+#include <vanetza/common/byte_order.hpp>
+#include <boost/units/quantity.hpp>
+#include <type_traits>
+
+namespace vanetza
+{
+
+template<typename T, ByteOrder ORDER>
+void serialize(OutputArchive& ar, EndianType<T, ORDER> value)
+{
+    typedef typename decltype(value)::network_type network_type;
+    T tmp = static_cast<network_type>(value).get();
+    ar << tmp;
+}
+
+template<typename T, ByteOrder ORDER>
+void deserialize(InputArchive& ar, EndianType<T, ORDER>& value)
+{
+    T tmp;
+    ar >> tmp;
+    value = network_cast<T>(tmp);
+}
+
+template<typename T>
+typename std::enable_if<std::is_integral<T>::value>::type
+serialize(OutputArchive& ar, T value)
+{
+    auto tmp = hton(value);
+    ar << tmp;
+}
+
+template<typename T>
+typename std::enable_if<std::is_integral<T>::value>::type
+deserialize(InputArchive& ar, T& value)
+{
+    T tmp;
+    ar >> tmp;
+    value = ntoh(tmp);
+}
+
+template<typename U, typename T>
+void serialize(OutputArchive& ar, boost::units::quantity<U, T> q)
+{
+    static_assert(std::is_integral<T>::value,
+            "Only integral based quantities are supported");
+    auto tmp = hton(q.value());
+    ar << tmp;
+}
+
+template<typename U, typename T>
+void deserialize(InputArchive& ar, boost::units::quantity<U, T>& q)
+{
+    static_assert(std::is_integral<T>::value,
+            "Only integral based quantities are supported");
+    T tmp;
+    ar >> tmp;
+    q = boost::units::quantity<U, T>::from_value(ntoh(tmp));
+}
+
+template<class T>
+typename std::enable_if<std::is_enum<T>::value>::type
+serialize(OutputArchive& ar, const T& t)
+{
+    serialize(ar, host_cast(static_cast<typename std::underlying_type<T>::type const>(t)));
+}
+
+template<class T>
+typename std::enable_if<std::is_enum<T>::value>::type
+deserialize(InputArchive& ar, T& t)
+{
+    typename std::underlying_type<T>::type tmp;
+    deserialize(ar, tmp);
+    t = static_cast<T>(tmp);
+}
+
+} // namespace vanetza
+
+#endif /* SERIALIZATION_HPP_U2YGHSPB */
+