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FLASHING.md says how to take a newer version of the colleague's tree (copy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

@@ -0,0 +1,86 @@
+#include <vanetza/common/position_fix.hpp>
+#include <vanetza/geodesy/country_database.hpp>
+#include <vanetza/geodesy/m49_code.hpp>
+#include <vanetza/asn1/security_profile.hpp>
+#include VANETZA_ASN1_SECURITY_HEADER(IdentifiedRegion.h)
+#include VANETZA_ASN1_SECURITY_HEADER(SequenceOfIdentifiedRegion.h)
+#include <vanetza/security/v3/asn1_types.hpp>
+#include <vanetza/security/v3/distance.hpp>
+#include <vanetza/security/v3/geometry.hpp>
+#include <vanetza/security/v3/location_checker.hpp>
+
+namespace vanetza
+{
+namespace security
+{
+namespace v3
+{
+
+bool AllowLocationChecker::valid_at_location(const asn1::EtsiTs103097Certificate&, const PositionFix&) const
+{
+    return true;
+}
+
+bool DenyLocationChecker::valid_at_location(const asn1::EtsiTs103097Certificate&, const PositionFix&) const
+{
+    return false;
+}
+
+bool DefaultLocationChecker::valid_at_location(const asn1::EtsiTs103097Certificate& cert, const PositionFix& location) const
+{
+    const asn1::GeographicRegion* region = cert.toBeSigned.region;
+    if (region) {
+        switch (region->present) {
+            case Vanetza_Security_GeographicRegion_PR_circularRegion:
+                return is_inside(location, region->choice.circularRegion);
+            case Vanetza_Security_GeographicRegion_PR_rectangularRegion:
+                return is_inside(location, region->choice.rectangularRegion);
+            case Vanetza_Security_GeographicRegion_PR_polygonalRegion:
+                return is_inside(location, region->choice.polygonalRegion);
+            case Vanetza_Security_GeographicRegion_PR_identifiedRegion:
+                return check_identified_region(location, region->choice.identifiedRegion);
+            default:
+                // unknown or future region restriction type — reject conservatively
+                return false;
+        }
+    } else {
+        // no region restriction applies
+        return true;
+    }
+}
+
+bool DefaultLocationChecker::check_identified_region(const PositionFix& location, const Vanetza_Security_SequenceOfIdentifiedRegion& seq) const
+{
+    if (!country_db_ || country_db_->empty())
+    {
+        // lacking database for country checks
+        return permissive_identified_region_;
+    }
+
+    // reject any region by default
+    bool accepted = false;
+
+    for (int i = 0; i < seq.list.count; ++i) {
+        const auto* entry = seq.list.array[i];
+        if (!entry) {
+            continue;
+        }
+
+        if (entry->present == Vanetza_Security_IdentifiedRegion_PR_countryOnly) {
+            geodesy::M49Code code(static_cast<uint16_t>(entry->choice.countryOnly));
+            geodesy::GeodeticPosition pos(location.latitude, location.longitude);
+            if (country_db_->is_inside(code, pos)) {
+                return true;
+            }
+        } else {
+            // may accept because of unsupported identified region
+            accepted = permissive_identified_region_;
+        }
+    }
+
+    return accepted;
+}
+
+} // namespace v3
+} // namespace security
+} // namespace vanetza