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/secured_message.cpp

@@ -0,0 +1,130 @@
+#include <vanetza/security/secured_message.hpp>
+#include <boost/variant/apply_visitor.hpp>
+#include <boost/variant/static_visitor.hpp>
+
+namespace vanetza
+{
+namespace security
+{
+
+SecuredMessageView::SecuredMessageView(const SecuredMessage& msg) :
+    m_variant(msg)
+{
+}
+
+struct ItsAidVisitor : boost::static_visitor<ItsAid>
+{
+    ItsAid operator()(const v2::SecuredMessage& msg) const
+    {
+        return get_its_aid(msg);
+    }
+
+    ItsAid operator()(const v3::SecuredMessage& msg) const
+    {
+        return msg.its_aid();
+    }
+};
+
+ItsAid get_its_aid(const SecuredMessage& msg)
+{
+    return boost::apply_visitor(ItsAidVisitor(), msg);
+}
+
+ItsAid get_its_aid(const SecuredMessageView& msg)
+{
+    return boost::apply_visitor(ItsAidVisitor(), msg);
+}
+
+std::size_t get_size(const SecuredMessage& msg)
+{
+    struct Visitor : boost::static_visitor<std::size_t>
+    {
+        std::size_t operator()(const v2::SecuredMessage& msg) const
+        {
+            return get_size(msg);
+        }
+
+        std::size_t operator()(const v3::SecuredMessage& msg) const
+        {
+            return msg.size();
+        }
+    };
+
+    return boost::apply_visitor(Visitor(), msg);
+}
+
+struct SerializeVisitor : boost::static_visitor<void>
+{
+    OutputArchive& m_archive;
+    SerializeVisitor(OutputArchive& ar) : m_archive(ar) {}
+
+    void operator()(const v2::SecuredMessage& msg)
+    {
+        serialize(m_archive, msg);
+    }
+
+    void operator()(const v3::SecuredMessage& msg)
+    {
+        serialize(m_archive, msg);
+    }
+};
+
+void serialize(OutputArchive& ar, const SecuredMessage& msg)
+{
+    SerializeVisitor visitor { ar };
+    boost::apply_visitor(visitor, msg);
+}
+
+void serialize(OutputArchive& ar, const SecuredMessageView& msg)
+{
+    SerializeVisitor visitor { ar };
+    boost::apply_visitor(visitor, msg);
+}
+
+std::size_t deserialize(InputArchive& ar, SecuredMessage& msg)
+{
+    struct Visitor : boost::static_visitor<std::size_t>
+    {
+        InputArchive& m_archive;
+        Visitor(InputArchive& ar) : m_archive(ar) {}
+
+        std::size_t operator()(v2::SecuredMessage& msg)
+        {
+            return deserialize(m_archive, msg);
+        }
+
+        std::size_t operator()(v3::SecuredMessage& msg)
+        {
+            return deserialize(m_archive, msg);
+        }
+    };
+
+    Visitor visitor(ar);
+    return boost::apply_visitor(visitor, msg);
+}
+
+struct PayloadCopyVisitor : boost::static_visitor<PacketVariant>
+{
+    PacketVariant operator()(const v2::SecuredMessage& msg) const
+    {
+        return msg.payload.data;
+    }
+
+    PacketVariant operator()(const v3::SecuredMessage& msg) const
+    {
+        return msg.payload();
+    }
+};
+
+PacketVariant get_payload_copy(const SecuredMessage& msg)
+{
+    return boost::apply_visitor(PayloadCopyVisitor(), msg);
+}
+
+PacketVariant get_payload_copy(const SecuredMessageView& msg)
+{
+    return boost::apply_visitor(PayloadCopyVisitor(), msg);
+}
+
+} // namespace security
+} // namespace vanetza