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/mapping.cpp

@@ -0,0 +1,36 @@
+#include "mapping.hpp"
+#include <stdexcept>
+
+namespace vanetza
+{
+namespace dcc
+{
+
+access::AccessCategory map_profile_onto_ac(Profile dp_id)
+{
+    access::AccessCategory ac = access::AccessCategory::BE;
+
+    switch (dp_id)
+    {
+        case Profile::DP0:
+            ac = access::AccessCategory::VO;
+            break;
+        case Profile::DP1:
+            ac = access::AccessCategory::VI;
+            break;
+        case Profile::DP2:
+            ac = access::AccessCategory::BE;
+            break;
+        case Profile::DP3:
+            ac = access::AccessCategory::BK;
+            break;
+        default:
+            throw std::invalid_argument("Invalid DCC Profile ID");
+            break;
+    }
+
+    return ac;
+}
+
+} // namespace dcc
+} // namespace vanetza