Keep vanetza-idf in obu-firmware, so a plain clone builds the firmware

obu-firmware builds against the vanetza-idf C-ITS library, which until now
came from the colleague's microbu-esp32c5 tree beside the repository and was
not tracked here, so a clone of this repository could not build the firmware
it ships. The library alone is now part of obu-firmware, as
obu-firmware/external/vanetza-idf: their external/vanetza-idf at commit
cf4b99f, unchanged (9775 files; see its PROVENANCE.md). CMake takes it from
there by default; -DVANETZA_IDF_DIR still points the build elsewhere.

The rest of the colleague's tree (their own VAM firmware, PKI tooling,
station-link Python tools, the V2X2MAP bridge) stays out of this repository
and gitignored; nothing is pushed to their repository. NOTES.md, docs/06,
TODO.md and the pcap verifier's usage line point at the new location.

obu-firmware/external/vanetza-idf/vanetza/security/v2/tests/subject_attribute.cpp

@@ -0,0 +1,47 @@
+#include <gtest/gtest.h>
+#include <vanetza/security/v2/subject_attribute.hpp>
+#include <vanetza/security/v2/tests/check_list.hpp>
+#include <vanetza/security/v2/tests/check_subject_attribute.hpp>
+#include <vanetza/security/tests/serialization.hpp>
+
+using namespace vanetza::security::v2;
+using vanetza::security::deserialize_from_hexstring;
+
+TEST(SubjectAttribute, serialize)
+{
+    std::list<SubjectAttribute> list;
+    list.push_back(create_random_verification_key(33));
+    list.push_back(create_random_encryption_key(34));
+    list.push_back(SubjectAssurance { 124 });
+    std::list<IntX> its_aid;
+    for (int i = 0; i < 4; ++i) {
+        its_aid.push_back(create_random_its_aid(i + 66));
+    }
+    list.push_back(its_aid);
+    std::list<ItsAidSsp> its_aid_ssp;
+    for (int i = 0; i < 1; ++i) {
+        its_aid_ssp.push_back(create_random_its_aid_ssp(i + 67));
+    }
+    list.push_back(its_aid_ssp);
+
+    check(list, serialize_roundtrip(list));
+}
+
+TEST(SubjectAttribute, WebValidator_ItsAidSsp)
+{
+    std::list<ItsAidSsp> list;
+    ItsAidSsp its1;
+    its1.its_aid.set(16512);
+    its1.service_specific_permissions = {0x01};
+    list.push_back(its1);
+
+    ItsAidSsp its2;
+    its2.its_aid.set(16513);
+    its2.service_specific_permissions = {0x01};
+    list.push_back(its2);
+
+    EXPECT_EQ(10, get_size(list));
+    std::list<ItsAidSsp> other_list;
+    deserialize_from_hexstring("0AC040800101C040810101", other_list);
+    check(list, other_list);
+}