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FLASHING.md says how to take a newer version of the colleague's tree (copy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/net/mac_address.hpp

@@ -0,0 +1,104 @@
+#ifndef MAC_ADDRESS_HPP_FDINBLBS
+#define MAC_ADDRESS_HPP_FDINBLBS
+
+#include <vanetza/common/serialization.hpp>
+#include <boost/operators.hpp>
+#include <boost/optional.hpp>
+#include <array>
+#include <cstddef>
+#include <cstdint>
+#include <initializer_list>
+#include <functional>
+#include <ostream>
+#include <string>
+
+namespace vanetza
+{
+
+class MacAddress : public boost::totally_ordered<MacAddress>
+{
+public:
+    static constexpr std::size_t length_bytes = 6;
+
+    MacAddress();
+    MacAddress(std::initializer_list<uint8_t> args);
+    MacAddress(const MacAddress&) = default;
+    MacAddress& operator=(const MacAddress&) = default;
+    MacAddress(MacAddress&&) = default;
+    MacAddress& operator=(MacAddress&&) = default;
+
+    std::array<uint8_t, length_bytes> octets;
+};
+
+extern const MacAddress cBroadcastMacAddress;
+bool operator==(const MacAddress& lhs, const MacAddress& rhs);
+bool operator<(const MacAddress& lhs, const MacAddress& rhs);
+std::ostream& operator<<(std::ostream& os, const MacAddress&);
+
+/**
+ * Try to parse MAC address from string
+ * \param str source string with "XX:XX:XX:XX:XX:XX" format
+ * \param addr pass parsed address by reference
+ * \return true if successfully parsed
+ */
+bool parse_mac_address(const std::string& str, MacAddress& addr);
+
+/**
+ * Try to parse MAC address from string
+ * \param str source string with "XX:XX:XX:XX:XX:XX" format
+ * \return parsed address if successful
+ */
+boost::optional<MacAddress> parse_mac_address(const std::string& str);
+
+/**
+ * Derive a MAC address from an arbitrary integral value.
+ * \param value used to derive MAC address, it's size does not matter
+ * \return New MAC address
+ */
+template<typename T>
+MacAddress create_mac_address(T value)
+{
+    MacAddress mac;
+    const std::size_t octets = std::min(mac.octets.size(), sizeof(T));
+    for (std::size_t i = 0; i < octets; ++i) {
+        mac.octets[i] = value >> (8 * (octets - i - 1)) & 0xff;
+    }
+    return mac;
+}
+
+/**
+ * Serialize MAC address
+ * \param out output sink
+ * \param addr MAC address
+ */
+void serialize(OutputArchive& out, const MacAddress& addr);
+
+/**
+ * Deserialize MAC address
+ * \param in input source
+ * \param addr deserialize into this object
+ */
+void deserialize(InputArchive& in, MacAddress& addr);
+
+} // namespace vanetza
+
+// specialization
+namespace std {
+
+template<>
+struct hash<vanetza::MacAddress>
+{
+    size_t operator()(const vanetza::MacAddress& addr) const
+    {
+        size_t tmp = 0;
+        for (auto octet : addr.octets) {
+            tmp ^= hash<decltype(octet)>()(octet);
+        }
+        return tmp;
+    }
+};
+
+} // namespace std
+
+#endif /* MAC_ADDRESS_HPP_FDINBLBS */
+