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FLASHING.md says how to take a newer version of the colleague's tree (copy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

@@ -0,0 +1,74 @@
+#include <vanetza/geonet/cbr_aggregator.hpp>
+#include <vanetza/geonet/location_table.hpp>
+#include <vanetza/geonet/loctex_g5.hpp>
+#include <algorithm>
+#include <array>
+
+namespace vanetza
+{
+namespace geonet
+{
+
+struct CbrAggregatorUnit
+{
+    CbrAggregatorUnit() : n(0) {}
+
+    void operator+=(dcc::ChannelLoad cbr)
+    {
+        // calculate average as double so numerator can be larger than 1.0 temporarily
+        average = dcc::ChannelLoad {(average.value() * n + cbr.value()) / (n + 1)};
+        ++n;
+
+        // >= comparison: second largest value might equal largest value
+        if (cbr >= maximum[0]) {
+            maximum[1] = maximum[0];
+            maximum[0] = cbr;
+        } else if (cbr > maximum[1]) {
+            maximum[1] = cbr;
+        }
+    }
+
+    dcc::ChannelLoad operator()(const dcc::ChannelLoad target) const
+    {
+        if (average > target) {
+            return maximum[0];
+        } else {
+            return maximum[1];
+        }
+    }
+
+    unsigned n;
+    dcc::ChannelLoad average;
+    std::array<dcc::ChannelLoad, 2> maximum;
+};
+
+CbrAggregator::CbrAggregator() :
+    m_one_hop_cbr(0.0), m_two_hop_cbr(0.0)
+{
+}
+
+void CbrAggregator::aggregate(ChannelLoad local, const LocationTable& lt, Timestamp lifetime, ChannelLoad target)
+{
+    m_local_cbr[1] = m_local_cbr[0];
+    m_local_cbr[0] = local;
+
+    CbrAggregatorUnit one_hop;
+    CbrAggregatorUnit two_hop;
+
+    LocationTable::entry_visitor entry_visitor =
+        [&](const MacAddress&, const LocationTableEntry& entry) {
+            const LocTEX_G5* loctex = entry.extensions.find<LocTEX_G5>();
+            if (loctex && loctex->local_update >= lifetime) {
+                one_hop += loctex->dcc_mco.local_cbr();
+                two_hop += loctex->dcc_mco.neighbour_cbr();
+            }
+        };
+    lt.visit(entry_visitor);
+
+    m_one_hop_cbr = one_hop(target);
+    m_two_hop_cbr = two_hop(target);
+    m_global_cbr = std::max({ m_local_cbr[1], m_one_hop_cbr, m_two_hop_cbr});
+}
+
+} // namespace geonet
+} // namespace vanetza