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/dcc/data_request.hpp

@@ -0,0 +1,29 @@
+#ifndef DATA_REQUEST_HPP_A5DWTTJN
+#define DATA_REQUEST_HPP_A5DWTTJN
+
+#include <vanetza/common/byte_order.hpp>
+#include <vanetza/common/clock.hpp>
+#include <vanetza/dcc/profile.hpp>
+#include <vanetza/net/mac_address.hpp>
+
+namespace vanetza
+{
+namespace dcc
+{
+
+struct DataRequest
+{
+    DataRequest() : dcc_profile(Profile::DP0) {}
+
+    uint16be_t ether_type;
+    MacAddress source;
+    MacAddress destination;
+    Profile dcc_profile;
+    Clock::duration lifetime;
+};
+
+} // namespace dcc
+} // namespace vanetza
+
+#endif /* DATA_REQUEST_HPP_A5DWTTJN */
+