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FLASHING.md says how to take a newer version of the colleague's tree (copy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

@@ -0,0 +1,90 @@
+#ifndef PUBLIC_KEY_HPP_DRZFSERF
+#define PUBLIC_KEY_HPP_DRZFSERF
+
+#include <vanetza/security/v2/ecc_point.hpp>
+#include <boost/variant/variant.hpp>
+
+namespace vanetza
+{
+namespace security
+{
+namespace v2
+{
+
+/// SymmetricAlgorithm specified in TS 103 097 v1.2.1, section 4.2.3
+enum class SymmetricAlgorithm : uint8_t
+{
+    AES128_CCM = 0
+};
+
+/// PublicKeyAlgorithm specified in TS 103 097 v1.2.1, section 4.2.2
+enum class PublicKeyAlgorithm : uint8_t
+{
+    ECDSA_NISTP256_With_SHA256 = 0,
+    ECIES_NISTP256 = 1
+};
+
+/// ecdsa_nistp256_with_sha256 specified in TS 103 097 v1.2.1, section 4.2.4
+struct ecdsa_nistp256_with_sha256
+{
+    EccPoint public_key;
+};
+
+/// ecies_nistp256 specified in TS 103 097 v1.2.1, section 4.2.4
+struct ecies_nistp256
+{
+    SymmetricAlgorithm supported_symm_alg;
+    EccPoint public_key;
+};
+
+/// Profile specified in TS 103 097 v1.2.1, section 4.2.4
+using PublicKey = boost::variant<ecdsa_nistp256_with_sha256, ecies_nistp256>;
+
+/**
+ * \brief Determines PublicKeyAlgorithm to a given PublicKey
+ * \param public_key
+ * \return algorithm type
+ */
+PublicKeyAlgorithm get_type(const PublicKey&);
+
+/**
+ * \brief Calculates size of a PublicKey
+ * \param public_key
+ * \return number of octets needed to serialize the PublicKey
+ */
+size_t get_size(const PublicKey&);
+
+/**
+ * \brief Deserializes a PublicKey from a binary archive
+ * \param ar with a serialized PublicKey at the beginning
+ * \param public_key to save deserialized values in
+ * \return size of the deserialized publicKey
+ */
+size_t deserialize(InputArchive&, PublicKey&);
+
+/**
+ * \brief Serializes a PublicKey into a binary archive
+ * \param ar to serialize in
+ * \param public_key to serialize
+ */
+void serialize(OutputArchive&, const PublicKey&);
+
+/**
+ * \brief Determines field size related to algorithm
+ * \param public_key_algorithm
+ * \return required buffer size for related fields
+ * */
+std::size_t field_size(PublicKeyAlgorithm);
+
+/**
+ * \brief Determines field size related to algorithm
+ * \param symmetric_algorithm
+ * \return required buffer size for related fields
+ */
+std::size_t field_size(SymmetricAlgorithm);
+
+} // namespace v2
+} // namespace security
+} // namespace vanetza
+
+#endif /* PUBLIC_KEY_HPP_DRZFSERF */