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FLASHING.md says how to take a newer version of the colleague's tree (copy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/dcc/state_machine_budget.hpp

@@ -0,0 +1,37 @@
+#ifndef STATE_MACHINE_BUDGET_HPP_9AL8A2JG
+#define STATE_MACHINE_BUDGET_HPP_9AL8A2JG
+
+#include <vanetza/common/clock.hpp>
+#include <boost/optional.hpp>
+
+namespace vanetza
+{
+
+// forward declarations
+class Runtime;
+namespace dcc { class StateMachine; }
+
+namespace dcc
+{
+
+/**
+ * StateMachineBudget: TRC restrictions as determined by a state machine
+ */
+class StateMachineBudget
+{
+public:
+    StateMachineBudget(const StateMachine&, const Runtime&);
+    Clock::duration delay();
+    void notify();
+
+private:
+    const StateMachine& m_fsm;
+    const Runtime& m_runtime;
+    boost::optional<Clock::time_point> m_last_tx;
+};
+
+} // namespace dcc
+} // namespace vanetza
+
+#endif /* STATE_MACHINE_BUDGET_HPP_9AL8A2JG */
+