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.cpp

@@ -0,0 +1,59 @@
+#include "data_confirm.hpp"
+#include "data_request.hpp"
+
+namespace vanetza
+{
+namespace geonet
+{
+
+DataConfirm& operator ^=(DataConfirm& lhs, DataConfirm::ResultCode rhs)
+{
+    if (rhs != DataConfirm::ResultCode::Accepted) {
+        lhs.result_code = rhs;
+    }
+    return lhs;
+}
+
+DataConfirm::ResultCode validate_data_request(const DataRequest& req, const MIB& mib)
+{
+    DataConfirm::ResultCode result = DataConfirm::ResultCode::Rejected_Unspecified;
+
+    // TODO: traffic class validation
+    if (req.maximum_lifetime > mib.itsGnMaxPacketLifetime) {
+        result = DataConfirm::ResultCode::Rejected_Max_Lifetime;
+    } else if (req.repetition && req.repetition->interval < mib.itsGnMinPacketRepetitionInterval) {
+        result = DataConfirm::ResultCode::Rejected_Min_Repetition_Interval;
+    } else {
+        result = DataConfirm::ResultCode::Accepted;
+    }
+
+    return result;
+}
+
+DataConfirm::ResultCode validate_data_request(const DataRequestWithArea& req, const MIB& mib)
+{
+    if (area_size(req.destination) > mib.itsGnMaxGeoAreaSize) {
+        return DataConfirm::ResultCode::Rejected_Max_Geo_Area_Size;
+    } else {
+        return validate_data_request(static_cast<const DataRequest&>(req), mib);
+    }
+}
+
+DataConfirm::ResultCode validate_payload(const std::unique_ptr<DownPacket>& payload, const MIB& mib)
+{
+    DataConfirm::ResultCode result = DataConfirm::ResultCode::Rejected_Unspecified;
+
+    if (!payload) {
+        // leave code to unspecified
+    } else if (payload->size() > mib.itsGnMaxSduSize) {
+        result = DataConfirm::ResultCode::Rejected_Max_SDU_Size;
+    } else {
+        result = DataConfirm::ResultCode::Accepted;
+    }
+
+    return result;
+}
+
+} // namespace geonet
+} // namespace vanetza
+