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FLASHING.md says how to take a newer version of the colleague's tree (copy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

@@ -0,0 +1,35 @@
+#pragma once
+
+#include <vanetza/geodesy/position.hpp>
+
+namespace vanetza
+{
+namespace geodesy
+{
+namespace haversine
+{
+
+/**
+ * Get distance between two geodetic positions using the Haversine formula.
+ * Uses a spherical Earth model (radius 6371 km).
+ * \param a first position
+ * \param b second position
+ * \return distance in meters (always positive)
+ */
+units::Length distance(const GeodeticPosition& a, const GeodeticPosition& b);
+
+/**
+ * Derive cartesian position ENU from geodetic coordinates using equirectangular projection.
+ * Uses a spherical Earth model (radius 6371 km).
+ * Suitable for short distances (< ~10 km) typical in GeoNetworking.
+ * \param origin Reference point becoming origin
+ * \param position Calculate cartesian coordinates for this point
+ * \return Cartesian coordinates of position relative to origin
+ */
+CartesianPosition local_cartesian(
+        const GeodeticPosition& origin,
+        const GeodeticPosition& position);
+
+} // namespace haversine
+} // namespace geodesy
+} // namespace vanetza