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FLASHING.md says how to take a newer version of the colleague's tree (copy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/facilities/detail/path_history.tpp

@@ -0,0 +1,63 @@
+#pragma once
+#include <vanetza/facilities/path_history.hpp>
+#include <vanetza/facilities/path_point.hpp>
+#include <chrono>
+#include <type_traits>
+
+namespace vanetza
+{
+namespace facilities
+{
+
+// C2C-CC BSP CAM trace limits (RS_BSP_318)
+static const units::Length cCamTraceMinLength = 200.0 * units::si::meter;
+static constexpr std::size_t cCamTraceMaxPoints = 23;
+
+template<typename SomePathSequence, typename SomePathPoint>
+void copy(const facilities::PathHistory& src, SomePathSequence& dest,
+        units::Length min_distance = cCamTraceMinLength, std::size_t max_points = cCamTraceMaxPoints)
+{
+    using SomePathDeltaTime = typename std::remove_pointer<decltype(SomePathPoint::pathDeltaTime)>::type;
+
+    static const auto scDeltaTimeStepLength = boost::posix_time::milliseconds(10);
+    static const auto scMaxDeltaTime = scDeltaTimeStepLength * 65535;
+
+    // ETSI TS 102 894-2: first PathPoint relative to the reference position, each subsequent
+    // one relative to the previous PathPoint (incremental deltas); newest first (RS_BSP_287).
+    facilities::PathPoint prev = src.getReferencePoint();
+    bool first_point = true; // only the first PathPoint may be clamped (stationary marker)
+
+    for (const PathPoint& point : src.getConcisePointsMinLength(min_distance, max_points)) {
+        auto delta_time = prev.time - point.time; // positive: point is in past
+        auto delta_latitude = round(point.latitude - prev.latitude, tenth_microdegree);
+        auto delta_longitude = round(point.longitude - prev.longitude, tenth_microdegree);
+
+        if (delta_latitude < -131071 || delta_latitude > 131071) {
+            continue; // delta latitude not encodable
+        } else if (delta_longitude < -131071 || delta_longitude > 131071) {
+            continue; // delta longitude not encodable
+        } else if (delta_time >= scDeltaTimeStepLength) {
+            if (delta_time > scMaxDeltaTime) {
+                if (first_point) {
+                    delta_time = scMaxDeltaTime; // RS_BSP_289: clamp the first PathPoint (stationary marker)
+                } else {
+                    break; // later overflow (old stationary) drops the disconnected older trail
+                }
+            }
+            SomePathPoint* path_point = asn1::allocate<SomePathPoint>();
+            path_point->pathPosition.deltaLatitude = delta_latitude;
+            path_point->pathPosition.deltaLongitude = delta_longitude;
+            path_point->pathPosition.deltaAltitude = DeltaAltitude::DeltaAltitude_unavailable;
+
+            path_point->pathDeltaTime = asn1::allocate<SomePathDeltaTime>();
+            *(path_point->pathDeltaTime) = delta_time.total_milliseconds() / scDeltaTimeStepLength.total_milliseconds();
+
+            ASN_SEQUENCE_ADD(&dest, path_point);
+            prev = point;
+            first_point = false;
+        }
+    }
+}
+
+} // namespace facilities
+} // namespace vanetza