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/hashed_id.cpp

@@ -0,0 +1,81 @@
+#include <vanetza/security/hashed_id.hpp>
+#include <boost/functional/hash.hpp>
+#include <algorithm>
+#include <cassert>
+#include <iomanip>
+#include <sstream>
+
+namespace vanetza
+{
+namespace security
+{
+
+HashedId3 truncate(const HashedId8& in)
+{
+    HashedId3 out;
+    assert(out.size() <= in.size());
+    std::copy_n(in.rbegin(), out.size(), out.rbegin());
+    return out;
+}
+
+HashedId8 create_hashed_id8(const Sha256Digest& digest)
+{
+    HashedId8 hashed;
+    std::copy(digest.end() - 8, digest.end(), hashed.data());
+    return hashed;
+}
+
+HashedId8 create_hashed_id8(const Sha384Digest& digest)
+{
+    HashedId8 hashed;
+    std::copy(digest.end() - 8, digest.end(), hashed.data());
+    return hashed;
+}
+
+std::string to_string(const vanetza::security::HashedId3& digest)
+{
+  std::stringstream ss;
+  ss << std::hex << std::setfill('0');
+  for (uint8_t octet : digest)
+  {
+    ss << std::setw(2) << static_cast<unsigned>(octet);
+  }
+  return ss.str();
+}
+
+std::string to_string(const vanetza::security::HashedId8& digest)
+{
+  std::stringstream ss;
+  ss << std::hex << std::setfill('0');
+  for (uint8_t octet : digest)
+  {
+    ss << std::setw(2) << static_cast<unsigned>(octet);
+  }
+  return ss.str();
+}
+
+} // namespace security
+} // namespace vanetza
+
+namespace std
+{
+
+size_t hash<vanetza::security::HashedId3>::operator()(const vanetza::security::HashedId3& hid3) const
+{
+    size_t seed = 0;
+    for (uint8_t octet : hid3) {
+        boost::hash_combine(seed, octet);
+    }
+    return seed;
+}
+
+size_t hash<vanetza::security::HashedId8>::operator()(const vanetza::security::HashedId8& hid8) const
+{
+    size_t seed = 0;
+    for (uint8_t octet : hid8) {
+        boost::hash_combine(seed, octet);
+    }
+    return seed;
+}
+
+} // namespace std