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/encryption_parameter.cpp

@@ -0,0 +1,91 @@
+#include <vanetza/security/exception.hpp>
+#include <vanetza/security/v2/encryption_parameter.hpp>
+#include <vanetza/security/v2/public_key.hpp>
+#include <boost/variant/apply_visitor.hpp>
+#include <boost/variant/static_visitor.hpp>
+
+namespace vanetza
+{
+namespace security
+{
+namespace v2
+{
+
+SymmetricAlgorithm get_type(const EncryptionParameter& param)
+{
+    struct Encryption_visitor : public boost::static_visitor<SymmetricAlgorithm>
+    {
+        SymmetricAlgorithm operator()(const Nonce&)
+        {
+            return SymmetricAlgorithm::AES128_CCM;
+        }
+    };
+
+    Encryption_visitor visit;
+    return boost::apply_visitor(visit, param);
+}
+
+void serialize(OutputArchive& ar, const EncryptionParameter& param)
+{
+    struct Encryption_visitor : public boost::static_visitor<>
+    {
+        Encryption_visitor(OutputArchive& ar) :
+            m_archive(ar)
+        {
+        }
+
+        void operator()(const Nonce& nonce)
+        {
+            for (auto& byte : nonce) {
+                m_archive << byte;
+            }
+        }
+
+        OutputArchive& m_archive;
+    };
+
+    SymmetricAlgorithm algo = get_type(param);
+    serialize(ar, algo);
+    Encryption_visitor visit(ar);
+    boost::apply_visitor(visit, param);
+}
+
+size_t get_size(const EncryptionParameter& param)
+{
+    size_t size = sizeof(SymmetricAlgorithm);
+    struct Encryption_visitor : public boost::static_visitor<size_t>
+    {
+        size_t operator()(const Nonce& nonce)
+        {
+            return nonce.size();
+        }
+    };
+
+    Encryption_visitor visit;
+    size += boost::apply_visitor(visit, param);
+    return size;
+}
+
+size_t deserialize(InputArchive& ar, EncryptionParameter& param)
+{
+    SymmetricAlgorithm algo;
+    deserialize(ar, algo);
+    switch (algo) {
+        case SymmetricAlgorithm::AES128_CCM: {
+            Nonce nonce;
+            for (size_t s = 0; s < nonce.size(); s++) {
+                ar >> nonce[s];
+            }
+            param = nonce;
+            break;
+        }
+        default:
+            throw deserialization_error("Unknown Symmetric Algorithm");
+            break;
+    }
+    return get_size(param);
+}
+
+} // namespace v2
+} // namespace security
+} // namespace vanetza