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/tools/socktap/gps_position_provider.hpp

@@ -0,0 +1,47 @@
+#ifndef GPS_POSITION_PROVIDER_HPP_GYN3GVQA
+#define GPS_POSITION_PROVIDER_HPP_GYN3GVQA
+
+#include "positioning.hpp"
+#include <vanetza/common/clock.hpp>
+#include <vanetza/common/position_provider.hpp>
+#include <boost/asio/io_context.hpp>
+#include <boost/asio/steady_timer.hpp>
+#include <string>
+#include <gps.h>
+
+class GpsPositionProvider : public vanetza::PositionProvider
+{
+public:
+    class GpsPositioningException : public PositioningException
+    {
+    protected:
+        GpsPositioningException(int);
+        friend class GpsPositionProvider;
+    };
+
+    GpsPositionProvider(boost::asio::io_context& io);
+    GpsPositionProvider(boost::asio::io_context& io, const std::string& hostname, const std::string& port);
+    ~GpsPositionProvider();
+
+    const vanetza::PositionFix& position_fix() override;
+    void fetch_position_fix();
+
+private:
+    void schedule_timer();
+    void on_timer(const boost::system::error_code& ec);
+    bool apply_gps_data(const gps_data_t&);
+
+    boost::asio::steady_timer timer_;
+    gps_data_t gps_data_;
+    vanetza::PositionFix fetched_position_fix_;
+};
+
+namespace gpsd
+{
+
+constexpr const char* default_port = DEFAULT_GPSD_PORT;
+constexpr const char* shared_memory = GPSD_SHARED_MEMORY;
+
+} // namespace gpsd
+
+#endif /* GPS_POSITION_PROVIDER_HPP_GYN3GVQA */