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FLASHING.md says how to take a newer version of the colleague's tree (copy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/data_request.cpp

@@ -0,0 +1,93 @@
+#include "data_request.hpp"
+#include <vanetza/btp/data_request.hpp>
+#include <vanetza/units/time.hpp>
+#include <boost/units/cmath.hpp>
+#include <stdexcept>
+
+namespace vanetza
+{
+namespace geonet
+{
+
+void decrement_by_one(DataRequest::Repetition& repetition)
+{
+    const auto zero = 0.0 * units::si::seconds;
+    if (repetition.maximum > zero && repetition.interval > zero
+        && repetition.maximum > repetition.interval) {
+        repetition.maximum = repetition.maximum - repetition.interval;
+
+    } else {
+        repetition.maximum = zero;
+    }
+}
+
+bool has_further_repetition(const DataRequest& request)
+{
+    bool repeat = false;
+    if (request.repetition) {
+        repeat = has_further_repetition(request.repetition.get());
+    }
+    return repeat;
+}
+
+bool has_further_repetition(const DataRequest::Repetition& repetition)
+{
+    const auto zero = 0.0 * units::si::seconds;
+    return repetition.maximum > zero && repetition.interval > zero &&
+        repetition.maximum >= repetition.interval;
+}
+
+struct access_request_visitor : public boost::static_visitor<DataRequest&>
+{
+    template<typename REQUEST>
+    DataRequest& operator()(REQUEST& request)
+    {
+        return request;
+    }
+};
+
+DataRequest& access_request(DataRequestVariant& variant)
+{
+    access_request_visitor visitor;
+    return boost::apply_visitor(visitor, variant);
+}
+
+void copy_request_parameters(const btp::DataRequestB& btp, DataRequest& gn)
+{
+    gn.upper_protocol = geonet::UpperProtocol::BTP_B;
+    gn.communication_profile = btp.gn.communication_profile;
+    gn.its_aid = btp.gn.its_aid;
+    if (btp.gn.maximum_lifetime) {
+        gn.maximum_lifetime = *btp.gn.maximum_lifetime;
+    }
+    gn.repetition = btp.gn.repetition;
+    if (btp.gn.maximum_hop_limit) {
+        gn.max_hop_limit = *btp.gn.maximum_hop_limit;
+    }
+    gn.traffic_class = btp.gn.traffic_class;
+}
+
+void copy_request_parameters(const btp::DataRequestB& btp, DataRequestWithAddress& gn)
+{
+    copy_request_parameters(btp, static_cast<DataRequest&>(gn));
+    const Address* address = boost::get<Address>(&btp.gn.destination);
+    if (address) {
+        gn.destination = *address;
+    } else {
+        throw std::runtime_error("BTP-B data request lacks destination address");
+    }
+}
+
+void copy_request_parameters(const btp::DataRequestB& btp, DataRequestWithArea& gn)
+{
+    copy_request_parameters(btp, static_cast<DataRequest&>(gn));
+    const Area* area = boost::get<Area>(&btp.gn.destination);
+    if (area) {
+        gn.destination = *area;
+    } else {
+        throw std::runtime_error("BTP-B data request lacks destination area");
+    }
+}
+
+} // namespace geonet
+} // namespace vanetza