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/v3/asn1_conversions.hpp

@@ -0,0 +1,39 @@
+#pragma once
+#include <vanetza/asn1/security_profile.hpp>
+#include VANETZA_ASN1_SECURITY_HEADER(HashedId3.h)
+#include VANETZA_ASN1_SECURITY_HEADER(HashedId8.h)
+#include <vanetza/security/ecc_point.hpp>
+#include <vanetza/security/hashed_id.hpp>
+#include <vanetza/security/v3/asn1_types.hpp>
+
+
+namespace vanetza
+{
+namespace security
+{
+
+HashedId8 create_hashed_id8(const Vanetza_Security_HashedId8_t&);
+HashedId3 create_hashed_id3(const Vanetza_Security_HashedId3_t&);
+
+namespace v3
+{
+
+HashedId8 convert(const Vanetza_Security_HashedId8_t&);
+
+/**
+ * Assign ByteBuffer content to an ASN.1 OCTET_STRING
+ * \param dst destination OCTET_STRING
+ * \param src source byte buffer
+ */
+void assign(OCTET_STRING_t* dst, const ByteBuffer& src);
+
+/**
+ * Convert an EccPoint to its ASN.1 EccP256CurvePoint representation
+ * \param point ECC point to convert
+ * \return ASN.1 EccP256CurvePoint
+ */
+asn1::EccP256CurvePoint to_asn1(const EccPoint& point);
+
+} // namespace v3
+} // namespace security
+} // namespace vanetza