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FLASHING.md says how to take a newer version of the colleague's tree (copy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/tools/fuzz-harness/router_fuzzing_context.cpp

@@ -0,0 +1,45 @@
+#include "router_fuzzing_context.hpp"
+
+namespace vanetza
+{
+
+class FuzzingRequestInterface : public dcc::RequestInterface
+{
+    void request(const dcc::DataRequest&, std::unique_ptr<ChunkPacket>) override {}
+};
+
+class FuzzingTransportInterface : public geonet::TransportInterface
+{
+    void indicate(const geonet::DataIndication&, std::unique_ptr<geonet::UpPacket>) override {}
+};
+
+RouterFuzzingContext::RouterFuzzingContext() :
+    runtime(vanetza::Clock::at("2010-12-23 18:29")),
+    security(runtime),
+    req_ifc(std::make_unique<FuzzingRequestInterface>()),
+    ind_ifc(std::make_unique<FuzzingTransportInterface>())
+{
+    initialize();
+}
+
+void RouterFuzzingContext::initialize()
+{
+    router = std::make_unique<geonet::Router>(runtime, mib);
+    router->set_security_entity(&security.entity());
+    router->set_access_interface(req_ifc.get());
+    router->set_transport_handler(geonet::UpperProtocol::BTP_B, ind_ifc.get());
+
+    geonet::Address gn_addr;
+    gn_addr.mid(MacAddress{0, 0, 0, 0, 0, 1});
+    router->set_address(gn_addr);
+}
+
+void RouterFuzzingContext::indicate(ByteBuffer&& buffer)
+{
+    MacAddress source { 0, 0, 0, 0, 0, 2 };
+    MacAddress destination { 0xff, 0xff, 0xff, 0xff, 0xff, 0xff };
+    auto packet = std::make_unique<geonet::UpPacket>(CohesivePacket { std::move(buffer), OsiLayer::Network });
+    router->indicate(std::move(packet), source, destination);
+}
+
+} // namespace vanetza