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/common/position_fix.hpp

@@ -0,0 +1,37 @@
+#ifndef POSITION_FIX_HPP_BGU14Q9D
+#define POSITION_FIX_HPP_BGU14Q9D
+
+#include <vanetza/common/clock.hpp>
+#include <vanetza/common/confident_quantity.hpp>
+#include <vanetza/common/position_confidence.hpp>
+#include <vanetza/units/angle.hpp>
+#include <vanetza/units/velocity.hpp>
+#include <vanetza/units/length.hpp>
+#include <boost/optional/optional.hpp>
+
+namespace vanetza
+{
+
+struct PositionFix
+{
+    Clock::time_point timestamp;
+    units::GeoAngle latitude;
+    units::GeoAngle longitude;
+    PositionConfidence confidence;
+    ConfidentQuantity<units::TrueNorth> course;
+    ConfidentQuantity<units::Velocity> speed;
+    boost::optional<ConfidentQuantity<units::Length>> altitude;
+};
+
+/**
+ * Check if PositionFix contains a horizontal (2D) position.
+ * At least latitude and longitude must be valid.
+ * \param posfix position fix to be checked
+ * \return true if horizontal position is valid
+ */
+bool has_horizontal_position(const PositionFix& posfix);
+
+} // namespace vanetza
+
+#endif /* POSITION_FIX_HPP_BGU14Q9D */
+