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/dcc_mco_field.hpp

@@ -0,0 +1,63 @@
+#ifndef DCC_MCO_FIELD_HPP_RLZ4PQMF
+#define DCC_MCO_FIELD_HPP_RLZ4PQMF
+
+#include <vanetza/common/bit_number.hpp>
+#include <vanetza/dcc/channel_load.hpp>
+#include <cstdint>
+
+namespace vanetza
+{
+namespace geonet
+{
+
+/**
+ * DCC-MCO (Multi Channel Operations) was introduced by TS 102 636-4-2 V1.1.1 and is carried
+ * forward unchanged by TS 103 836-4-2 V2.1.1 clause 6.3.3 Table 3 (Release 2): Octet 40
+ * CBR_L_0_Hop = floor(CBR_L_0_Hop x 255), Octet 41 CBR_L_1_Hop likewise, Octet 42 bits 0-4 TX
+ * power [0;31] dBm, Octet 43 reserved. This field layout was cross-checked bit-for-bit against
+ * the current V2.1.1 text; only this docstring's citation was stale.
+ * DccMcoField implements the SHB header field extension.
+ */
+class DccMcoField
+{
+public:
+    using ChannelLoad = dcc::ChannelLoad;
+
+    DccMcoField();
+
+    // copy operations
+    DccMcoField(const DccMcoField&) = default;
+    DccMcoField& operator=(const DccMcoField&) = default;
+
+    // conversion from/to 4 bytes (host byte order)
+    explicit DccMcoField(uint32_t);
+    DccMcoField& operator=(uint32_t);
+    explicit operator uint32_t() const;
+
+    void local_cbr(const ChannelLoad&);
+    ChannelLoad local_cbr() const;
+
+    void neighbour_cbr(const ChannelLoad&);
+    ChannelLoad neighbour_cbr() const;
+
+    /**
+     * Output power of packet transmission
+     * \return [0; 31] dBm (values are cramped at limits)
+     */
+    void output_power(unsigned dbm);
+    unsigned output_power() const;
+
+private:
+    using cbr_type = uint8_t;
+    using power_type = BitNumber<unsigned, 5>;
+
+    cbr_type m_cbr_l0_hop; /*< local CBR measurement */
+    cbr_type m_cbr_l1_hop; /*< maximum CBR measurement from 1-hop neighbours */
+    power_type m_output_power; /*< output power of packet transmission */
+};
+
+} // namespace geonet
+} // namespace vanetza
+
+#endif /* DCC_MCO_FIELD_HPP_RLZ4PQMF */
+