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/fully_meshed_state_machine.hpp

@@ -0,0 +1,105 @@
+#ifndef FULLY_MESHED_STATE_MACHINE_HPP_YPE958OH
+#define FULLY_MESHED_STATE_MACHINE_HPP_YPE958OH
+
+#include <vanetza/common/clock.hpp>
+#include <vanetza/dcc/channel_load.hpp>
+#include <vanetza/dcc/state_machine.hpp>
+#include <boost/circular_buffer.hpp>
+#include <boost/optional.hpp>
+
+namespace vanetza
+{
+namespace dcc
+{
+
+// constants
+static constexpr Clock::duration NDL_minDccSampling = std::chrono::milliseconds(100);
+
+
+class State
+{
+public:
+    virtual Clock::duration transmission_interval() const = 0;
+    virtual const char* name() const = 0;
+    virtual ~State() {}
+};
+
+class Relaxed : public State
+{
+public:
+    Clock::duration transmission_interval() const override;
+    const char* name() const override;
+};
+
+class Active : public State
+{
+public:
+    Active();
+    void update(double min, double max);
+    Clock::duration transmission_interval() const override;
+    const char* name() const override;
+
+private:
+    static const std::size_t sc_substates;
+    std::size_t m_substate;
+};
+
+class Restrictive : public State
+{
+public:
+    Clock::duration transmission_interval() const override;
+    const char* name() const override;
+};
+
+/**
+ * Fully meshed TRC state machine as per TS 102 687 v1.1.1
+ *
+ * States are modelled according to C2C-CC DCC Whitepaper / BSP v1.2
+ * State transitions are deferred internally for ramping up and cooling down over time.
+ */
+class FullyMeshedStateMachine : public StateMachine
+{
+public:
+    FullyMeshedStateMachine();
+    ~FullyMeshedStateMachine();
+
+    /**
+     * Notify state machine about current channel load.
+     * This method expects to be called in regular intervals
+     * of NDL_minDccSampling length.
+     */
+    void update(ChannelLoad channel_load);
+
+    /**
+     * Get currently allowed maximum message rate depending on state
+     * \return messages per second
+     */
+    double message_rate() const;
+
+    /**
+     * Get advised transmission interval between consecutive messages
+     * \return message transmission interval
+     */
+    Clock::duration transmission_interval() const;
+
+    /**
+     * Get state machine's active state
+     */
+    const State& state() const;
+
+private:
+    double max_channel_load() const;
+    double min_channel_load() const;
+
+    Relaxed m_relaxed;
+    Active m_active;
+    Restrictive m_restrictive;
+    State* m_state;
+    boost::circular_buffer<ChannelLoad> m_channel_loads;
+};
+
+} // namespace dcc
+} // namespace vanetza
+
+#endif /* FULLY_MESHED_STATE_MACHINE_HPP_YPE958OH */
+