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FLASHING.md says how to take a newer version of the colleague's tree (copy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

@@ -0,0 +1,81 @@
+#ifndef TIMESTAMP_HPP_SFETMZJI
+#define TIMESTAMP_HPP_SFETMZJI
+
+#include <vanetza/common/clock.hpp>
+#include <vanetza/geonet/serialization.hpp>
+#include <cstdint>
+#include <boost/operators.hpp>
+#include <boost/date_time/posix_time/posix_time.hpp>
+#include <boost/units/absolute.hpp>
+#include <boost/units/quantity.hpp>
+#include <boost/units/systems/si/time.hpp>
+#include <boost/units/make_scaled_unit.hpp>
+
+namespace vanetza
+{
+namespace geonet
+{
+
+class Timestamp : public boost::totally_ordered<Timestamp>
+{
+public:
+    typedef uint32_t value_type;
+    typedef boost::units::make_scaled_unit<
+                boost::units::si::time,
+                boost::units::scale<10, boost::units::static_rational<-3>>
+            >::type unit_type;
+    typedef boost::units::absolute<unit_type> absolute_unit_type;
+    typedef boost::units::quantity<absolute_unit_type, value_type> time_type;
+    typedef boost::units::quantity<unit_type, value_type> duration_type;
+
+    static unit_type millisecond();
+    static boost::posix_time::ptime start_time();
+
+    Timestamp() : m_timestamp(0) {}
+    Timestamp(time_type t) : m_timestamp(t) {}
+    Timestamp(const Clock::time_point&);
+    Timestamp(const boost::posix_time::ptime&);
+    value_type raw() const { return m_timestamp.value(); }
+    time_type quantity() const { return m_timestamp; }
+    Timestamp& operator+=(duration_type);
+    Timestamp& operator-=(duration_type);
+
+    /**
+     * Timestamp is before other one
+     * \param other time stamp
+     * \return true if other timestamp is later
+     */
+    bool before(const Timestamp& other) const;
+
+    /**
+     * Timestamp is after other one
+     * \param other time stamp
+     * \return true is other timestamp is before
+     */
+    bool after(const Timestamp& other) const;
+
+private:
+    time_type m_timestamp; // since 01-01-2004 00:00:00.0
+};
+
+// timestamp calculus
+Timestamp operator+(Timestamp lhs, Timestamp::duration_type rhs);
+Timestamp operator-(Timestamp lhs, Timestamp::duration_type rhs);
+Timestamp::duration_type operator-(Timestamp lhs, Timestamp rhs);
+
+// timestamp comparison according to ETSI GeoNet
+bool is_greater(Timestamp lhs, Timestamp rhs);
+
+// operators required for boost::totally_ordered
+bool operator<(Timestamp lhs, Timestamp rhs);
+bool operator==(Timestamp lhs, Timestamp rhs);
+
+// serialization
+void serialize(const Timestamp&, OutputArchive&);
+void deserialize(Timestamp&, InputArchive&);
+
+} // namespace geonet
+} // namespace vanetza
+
+#endif /* TIMESTAMP_HPP_SFETMZJI */
+