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/tools/pki/openssl_security_module.hpp

@@ -0,0 +1,44 @@
+#pragma once
+
+#include "security_module.hpp"
+#include <boost/optional/optional.hpp>
+
+namespace vanetza
+{
+namespace pki
+{
+
+class CredentialStorage;
+
+class OpenSslSecurityModule : public SecurityModule
+{
+public:
+    OpenSslSecurityModule(std::shared_ptr<CredentialStorage>);
+
+    Sha256Hash calculate_sha256_hash(const std::uint8_t* buffer, std::size_t length) override;
+    Sha384Hash calculate_sha384_hash(const std::uint8_t* buffer, std::size_t length) override;
+    bool verify(const Sha256Hash&, const Signature&, const PublicKey&) override;
+    bool verify(const Sha384Hash&, const Signature&, const PublicKey&) override;
+    ByteBuffer generate_nonce(std::size_t length) override;
+    std::unique_ptr<EciesContext> create_ecies_context(const PublicKey& receiver, const Sha256Hash& info) override;
+    ByteBuffer calculate_hmac_sha256(const ByteBuffer& key, const ByteBuffer& data) override;
+
+    boost::optional<Signature> sign(const ByteBuffer& data, const PublicKey&) override;
+
+    /**
+     * Creates a new public and private key pair.
+     * The private key is intentionally not returned but only stored in the credential storage.
+     */
+    PublicKey create_key(KeyType) override;
+
+    bool discard_key(const PublicKey&) override;
+
+private:
+    bool verify(const uint8_t* digest, std::size_t dlen, const Signature&, const PublicKey&);
+    boost::optional<Signature> sign(const ByteBuffer&, const PrivateKey&);
+
+    std::shared_ptr<CredentialStorage> m_credential_storage;
+};
+
+} // namespace pki
+} // namespace vanetza