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.hpp

@@ -0,0 +1,58 @@
+#ifndef ENCRYPTION_PARAMETER_HPP_EIAWNAWY
+#define ENCRYPTION_PARAMETER_HPP_EIAWNAWY
+
+#include <vanetza/security/v2/serialization.hpp>
+#include <boost/variant/variant.hpp>
+#include <array>
+#include <cstdint>
+
+namespace vanetza
+{
+namespace security
+{
+namespace v2
+{
+
+/// forward declaration, see public_key.hpp
+enum class SymmetricAlgorithm : uint8_t;
+
+/// Nonce specified in TS 103 097 v1.2.1, section 4.2.7
+using Nonce = std::array<uint8_t, 12>;
+
+/// EncryptionParameter specified in TS 103 097 v1.2.1, section 4.2.7
+using EncryptionParameter = boost::variant<Nonce>;
+
+/**
+ * \brief Determines SymmetricAlgorithm for an EncryptionParameter
+ * \param param
+ * \return SymmetricAlgorithm
+ */
+SymmetricAlgorithm get_type(const EncryptionParameter&);
+
+/**
+ * \brief Serializes an EncryptionParameter into a binary archive
+ * \param ar to serialize in
+ * \param param to serialize
+ */
+void serialize(OutputArchive&, const EncryptionParameter&);
+
+/**
+ * \brief Calculates size of an EncryptionParameter
+ * \param param
+ * \return number of octets needed to serialize the EncryptionParameter
+ */
+size_t get_size(const EncryptionParameter&);
+
+/**
+ * \brief Deserializes an EncryptionParameter from a binary archive
+ * \param ar Input expected to start with an EncryptionParameter
+ * \param enc Deserialized encryption parameter
+ * \return size of deserialized EncryptionParameter
+ */
+size_t deserialize(InputArchive&, EncryptionParameter&);
+
+} // namespace v2
+} // namespace security
+} // namespace vanetzta
+
+#endif /* ENCRYPTION_PARAMETER_HPP_EIAWNAWY */