Keep the colleague's microbu-esp32c5 tree in this repository

obu-firmware builds against vanetza-idf from microbu-esp32c5/external, but
that tree was gitignored, so a clone of this repository could not build the
firmware it ships. It is now committed here as ordinary files in its own
folder, microbu-esp32c5/: the colleague's commit cf4b99f plus the V2X2MAP
bridge's signature verification (--trust) used on the bench. Nothing is
fetched from or pushed to the colleague's repository; this repository and
its remotes carry everything. The folder's own .gitignore keeps build output,
downloaded components and private key material out, as it did there; the
committed file set is identical to that repository's tracked files.

The ESP32-C5 is still flashed from obu-firmware/, which only takes
vanetza-idf from microbu-esp32c5/, so the two stay separate folders.
FLASHING.md says how to take a newer version of the colleague's tree (copy
it over the folder, rebuild, test, commit).

microbu-esp32c5/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 */
+