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/validation.hpp

@@ -0,0 +1,40 @@
+#pragma once
+
+#include "sha.hpp"
+#include <vanetza/asn1/security/EtsiTs103097Data.h>
+#include <vanetza/common/byte_buffer.hpp>
+
+namespace vanetza
+{
+namespace pki
+{
+
+class Certificate;
+class CertificateStorage;
+class HashedId8;
+class SecurityModule;
+
+bool validate(SecurityModule&, const Vanetza_Security_EtsiTs103097Data_t&, const Certificate&);
+bool validate(SecurityModule&, const Vanetza_Security_SignedData_t&, const Vanetza_Security_Certificate_t&);
+
+// True iff the response's requestHash echoes the request: the leftmost 16 octets of the request's SHA-256
+bool check_request_hash(const Sha256Hash& request_digest, const ByteBuffer& response_hash);
+
+const Vanetza_Security_SignedData_t* get_signed_data(const Vanetza_Security_EtsiTs103097Data_t&);
+const Vanetza_Security_Opaque_t* get_unsecured_data(const Vanetza_Security_EtsiTs103097Data_t&);
+bool signed_by(SecurityModule&, const Vanetza_Security_SignedData_t&, const HashedId8&);
+HashAlgorithm get_hash_algorithm(const Vanetza_Security_SignedData_t&);
+
+template<typename Hash>
+Hash calculate_digest(SecurityModule&, const Vanetza_Security_ToBeSignedData_t&, const Vanetza_Security_Certificate_t*);
+
+template<>
+Sha256Hash calculate_digest(SecurityModule&, const Vanetza_Security_ToBeSignedData_t&,
+    const Vanetza_Security_Certificate_t*);
+
+template<>
+Sha384Hash calculate_digest(SecurityModule&, const Vanetza_Security_ToBeSignedData_t&,
+    const Vanetza_Security_Certificate_t*);
+
+} // namespace pki
+} // namespace vanetza