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FLASHING.md says how to take a newer version of the colleague's tree (copy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/security/v3/boost_geometry.hpp

@@ -0,0 +1,94 @@
+#pragma once
+#include <vanetza/security/v3/asn1_types.hpp>
+#include <boost/geometry/core/closure.hpp>
+#include <boost/geometry/core/cs.hpp> 
+#include <boost/geometry/geometries/point.hpp>
+#include <boost/iterator/iterator_facade.hpp>
+
+namespace vanetza
+{
+
+// forward declaration
+struct PositionFix;
+
+namespace security
+{
+namespace v3
+{
+
+/**
+ * TwoDLocationModel is a Boost.Geometry point model representing a 2D geographic location.
+ */
+using TwoDLocationModel = boost::geometry::model::point<double, 2, boost::geometry::cs::geographic<boost::geometry::degree>>;
+
+/**
+ * \brief Create a TwoDLocationModel from an ASN.1 TwoDLocation.
+ *
+ * \param location The ASN.1 TwoDLocation_t structure to convert.
+ * \return A TwoDLocationModel representing the geographic location.
+ */
+TwoDLocationModel make_model(const asn1::TwoDLocation& location);
+TwoDLocationModel make_model(const PositionFix&);
+
+/**
+ * TwoDLocationIterator allows traversal of ASN.1 PolygonalRegion providing TwoDLocationModel objects.
+ */
+class TwoDLocationIterator :
+    public boost::iterator_facade<TwoDLocationIterator,
+        TwoDLocationModel,
+        boost::random_access_traversal_tag,
+        TwoDLocationModel>
+{
+public:
+    TwoDLocationIterator() = default;
+    explicit TwoDLocationIterator(const asn1::PolygonalRegion& region, std::size_t index);
+
+private:
+    friend class boost::iterator_core_access;
+
+    void increment();
+    void decrement();
+    void advance(std::size_t n);
+    std::ptrdiff_t distance_to(const TwoDLocationIterator& other) const;
+    bool equal(const TwoDLocationIterator& other) const;
+    TwoDLocationModel dereference() const;
+
+    const asn1::PolygonalRegion* m_region = nullptr;
+    std::size_t m_index = 0;
+};
+
+/**
+ * \brief Adapt ASN.1 PolygonalRegion to a Boost.Geometry ring.
+ */
+class PolygonalRegionRingAdapter
+{
+public:
+    using iterator = TwoDLocationIterator;
+    using const_iterator = TwoDLocationIterator;
+
+    PolygonalRegionRingAdapter(const asn1::PolygonalRegion& region);
+    iterator begin() const;
+    iterator end() const;
+    std::size_t size() const;
+
+private:
+    const asn1::PolygonalRegion& m_region;
+};
+
+} // namespace v3
+} // namespace security
+} // namespace vanetza
+
+namespace boost
+{
+namespace geometry
+{
+namespace traits
+{
+
+template<> struct tag<vanetza::security::v3::PolygonalRegionRingAdapter> { using type = ring_tag; };
+template<> struct closure<vanetza::security::v3::PolygonalRegionRingAdapter> { static const closure_selector value = open; };
+
+} // namespace traits
+} // namespace gemoetry
+} // namespace boost