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FLASHING.md says how to take a newer version of the colleague's tree (copy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/v2/signer_info.hpp

@@ -0,0 +1,107 @@
+#ifndef SIGNER_INFO_HPP_9K6GXK4R
+#define SIGNER_INFO_HPP_9K6GXK4R
+
+#include <vanetza/security/v2/basic_elements.hpp>
+#include <vanetza/security/v2/public_key.hpp>
+#include <boost/variant/recursive_wrapper.hpp>
+#include <boost/variant/variant.hpp>
+#include <cstddef>
+#include <cstdint>
+#include <list>
+
+namespace vanetza
+{
+namespace security
+{
+namespace v2
+{
+
+struct Certificate;
+
+/// described in TS 103 097 v1.2.1, section 4.2.11
+enum class SignerInfoType : uint8_t
+{
+    Self = 0,                                   // nothing -> nullptr_t
+    Certificate_Digest_With_SHA256 = 1,         // HashedId8
+    Certificate = 2,                            // Certificate
+    Certificate_Chain = 3,                      // std::list<Certificate>
+    Certificate_Digest_With_Other_Algorithm = 4 // CertificateDigestWithOtherAlgorithm
+};
+
+/// described in TS 103 097 v1.2.1, section 4.2.10
+struct CertificateDigestWithOtherAlgorithm
+{
+    PublicKeyAlgorithm algorithm;
+    HashedId8 digest;
+};
+
+/// described in TS 103 097 v1.2.1, section 4.2.10
+using SignerInfo = boost::variant<
+    std::nullptr_t,
+    HashedId8,
+    boost::recursive_wrapper<Certificate>,
+    std::list<Certificate>,
+    CertificateDigestWithOtherAlgorithm
+>;
+
+/**
+ * \brief Determines SignerInfoType of SignerInfo
+ * \param SignerInfo
+ * \return SignerInfoType
+ */
+SignerInfoType get_type(const SignerInfo&);
+
+/**
+ * \brief Calculates size of an CertificateDigestWithOtherAlgorithm
+ * \param CertificateDigestWithOtherAlgorithm
+ * \return number of octets needed to serialize the CertificateDigestWithOtherAlgorithm
+ */
+size_t get_size(const CertificateDigestWithOtherAlgorithm&);
+
+/**
+ * \brief Calculates size of an SignerInfo
+ * \param SignerInfo
+ * \return number of octets needed to serialize the SignerInfo
+ */
+size_t get_size(const SignerInfo&);
+
+/**
+ * \brief Serializes an CertificateDigestWithOtherAlgorithm into a binary archive
+ */
+void serialize(OutputArchive&, const CertificateDigestWithOtherAlgorithm&);
+
+/**
+ * \brief Serializes an SignerInfo into a binary archive
+ */
+void serialize(OutputArchive&, const SignerInfo&);
+
+/**
+ * \brief Deserializes an CertificateDigestWithOtherAlgorithm from a binary archive
+ * \param archive with a CertificateDigestWithOtherAlgorithm at the beginning
+ * \param CertificateDigestWithOtherAlgorithm to deserialize
+ * \return size of the deserialized CertificateDigestWithOtherAlgorithm
+ */
+size_t deserialize(InputArchive&, CertificateDigestWithOtherAlgorithm&);
+
+/**
+ * \brief Deserializes an SignerInfo from a binary archive
+ * \param archive with a SignerInfo at the beginning
+ * \param SignerInfo to deserialize
+ * \return size of the deserialized SignerInfo
+ */
+size_t deserialize(InputArchive&, SignerInfo&);
+
+/**
+ * \brief Deserialize SignerInfo of a Certificate from a binary archive
+ * This function rejects SignerInfo types which are invalid for certificates.
+ * \param ar archive with a (legal) SignerInfo at the beginning
+ * \param info SignerInfo to deserialize
+ * \return size of the deserialized SignerInfo
+ */
+size_t deserialize_certificate_signer(InputArchive& ar, SignerInfo& info);
+
+} // namespace v2
+} // namespace security
+} // namespace vanetza
+
+#endif /* SIGNER_INFO_HPP_9K6GXK4R */