Keep the colleague's microbu-esp32c5 tree in this repository

obu-firmware builds against vanetza-idf from microbu-esp32c5/external, but
that tree was gitignored, so a clone of this repository could not build the
firmware it ships. It is now committed here as ordinary files in its own
folder, microbu-esp32c5/: the colleague's commit cf4b99f plus the V2X2MAP
bridge's signature verification (--trust) used on the bench. Nothing is
fetched from or pushed to the colleague's repository; this repository and
its remotes carry everything. The folder's own .gitignore keeps build output,
downloaded components and private key material out, as it did there; the
committed file set is identical to that repository's tracked files.

The ESP32-C5 is still flashed from obu-firmware/, which only takes
vanetza-idf from microbu-esp32c5/, so the two stay separate folders.
FLASHING.md says how to take a newer version of the colleague's tree (copy
it over the folder, rebuild, test, commit).

microbu-esp32c5/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