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/geonet/data_confirm.hpp

@@ -0,0 +1,52 @@
+#ifndef DATA_CONFIRM_HPP_Z1WCMN8T
+#define DATA_CONFIRM_HPP_Z1WCMN8T
+
+#include <vanetza/geonet/mib.hpp>
+#include <vanetza/geonet/packet.hpp>
+#include <memory>
+
+namespace vanetza
+{
+namespace geonet
+{
+
+struct DataRequest;
+struct DataRequestWithArea;
+
+struct DataConfirm
+{
+    enum class ResultCode {
+        Accepted,
+        Rejected_Max_SDU_Size,
+        Rejected_Max_Lifetime,
+        Rejected_Min_Repetition_Interval,
+        Rejected_Unsupported_Traffic_Class,
+        Rejected_Max_Geo_Area_Size,
+        Rejected_Unspecified
+    };
+
+    DataConfirm() : result_code(ResultCode::Accepted) {}
+    DataConfirm(ResultCode code) : result_code(code) {}
+    bool accepted() const { return result_code == ResultCode::Accepted; }
+    bool rejected() const { return !accepted(); }
+    ResultCode result_code;
+};
+
+/**
+ * XOR result code with DataConfirm's result code.
+ * Replaces result code of DataConfirm only if new code is an error code.
+ * \param lhs Operate on this DataConfirm
+ * \param rhs XOR this ResultCode with lhs
+ * \return reference to modified DataConfirm
+ */
+DataConfirm& operator ^=(DataConfirm& lhs, DataConfirm::ResultCode rhs);
+
+DataConfirm::ResultCode validate_data_request(const DataRequest&, const MIB&);
+DataConfirm::ResultCode validate_data_request(const DataRequestWithArea&, const MIB&);
+DataConfirm::ResultCode validate_payload(const std::unique_ptr<DownPacket>&, const MIB&);
+
+} // namespace geonet
+} // namespace vanetza
+
+#endif /* DATA_CONFIRM_HPP_Z1WCMN8T */
+