Keep vanetza-idf in obu-firmware, so a plain clone builds the firmware

obu-firmware builds against the vanetza-idf C-ITS library, which until now
came from the colleague's microbu-esp32c5 tree beside the repository and was
not tracked here, so a clone of this repository could not build the firmware
it ships. The library alone is now part of obu-firmware, as
obu-firmware/external/vanetza-idf: their external/vanetza-idf at commit
cf4b99f, unchanged (9775 files; see its PROVENANCE.md). CMake takes it from
there by default; -DVANETZA_IDF_DIR still points the build elsewhere.

The rest of the colleague's tree (their own VAM firmware, PKI tooling,
station-link Python tools, the V2X2MAP bridge) stays out of this repository
and gitignored; nothing is pushed to their repository. NOTES.md, docs/06,
TODO.md and the pcap verifier's usage line point at the new location.

obu-firmware/external/vanetza-idf/vanetza/facilities/path_point.hpp

@@ -0,0 +1,37 @@
+#ifndef PATH_POINT_HPP_LXQ9YZKI
+#define PATH_POINT_HPP_LXQ9YZKI
+
+#include <vanetza/units/angle.hpp>
+#include <vanetza/units/length.hpp>
+#include <boost/date_time/posix_time/posix_time.hpp>
+
+namespace vanetza
+{
+namespace facilities
+{
+
+extern const units::Length cREarthMeridian;
+
+struct PathPoint
+{
+    PathPoint();
+
+    units::GeoAngle latitude;
+    units::GeoAngle longitude;
+    units::Angle heading;
+    boost::posix_time::ptime time;
+};
+
+/**
+ * Calculate chord length between two points
+ * \param path point A
+ * \param path point B
+ * \return chord length
+ */
+units::Length chord_length(const PathPoint&, const PathPoint&);
+
+} // namespace facilities
+} // namespace vanetza
+
+#endif /* PATH_POINT_HPP_LXQ9YZKI */
+