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FLASHING.md says how to take a newer version of the colleague's tree (copy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

@@ -0,0 +1,102 @@
+#ifndef SIGNATURE_HPP_ZWPLNDVE
+#define SIGNATURE_HPP_ZWPLNDVE
+
+#include <vanetza/security/signature.hpp>
+#include <vanetza/security/v2/ecc_point.hpp>
+#include <vanetza/security/v2/public_key.hpp>
+#include <vanetza/security/v2/serialization.hpp>
+#include <boost/optional/optional.hpp>
+#include <boost/variant/variant.hpp>
+
+namespace vanetza
+{
+namespace security
+{
+namespace v2
+{
+
+struct Signature {
+    SomeEcdsaSignature some_ecdsa;
+
+    Signature() = default;
+
+    Signature(EcdsaSignature&& sig) : some_ecdsa(std::move(sig)) {}
+    Signature& operator=(EcdsaSignature&& sig) { some_ecdsa = std::move(sig); return *this; }
+
+    Signature(const EcdsaSignature& sig) : some_ecdsa(sig) {}
+    Signature& operator=(const EcdsaSignature& sig) { some_ecdsa = sig; return *this; }
+
+    Signature(EcdsaSignatureFuture&& sig) : some_ecdsa(std::move(sig)) {}
+    Signature& operator=(EcdsaSignatureFuture&& sig) { some_ecdsa = std::move(sig); return *this; }
+
+    Signature(SomeEcdsaSignature&& some) : some_ecdsa(std::move(some)) {}
+    Signature& operator=(SomeEcdsaSignature&& some) { this->some_ecdsa = std::move(some); return *this; }
+};
+
+/**
+ * brief Determines PublicKeyAlgorithm of a given Signature
+ * \param signature
+ * \return PublicKeyAlgorithm
+ */
+PublicKeyAlgorithm get_type(const Signature&);
+
+/**
+ * \brief Calculates size of a EcdsaSignature
+ * \param signature
+ * \return number of octets needed for serialization
+ */
+size_t get_size(const EcdsaSignature&);
+
+/**
+ * \brief Calculates size of a EcdsaSignatureFuture
+ * \param signature
+ * \return number of octets needed for serialization
+ */
+size_t get_size(const EcdsaSignatureFuture&);
+
+/**
+ * \brief Calculates size of a Signature
+ * \param signature
+ * \return number of octets needed for serialization
+ */
+size_t get_size(const Signature&);
+
+/**
+ * \brief Serializes a signature into a binary archive
+ * \param ar to serialize in
+ * \param signature
+ */
+void serialize(OutputArchive&, const Signature&);
+void serialize(OutputArchive&, const EcdsaSignature&);
+void serialize(OutputArchive&, const EcdsaSignatureFuture&);
+
+/**
+ * \brief Deserializes an EcdsaSignature from a binary archive
+ *  Requires PublicKeyAlgorithm for determining the signature size
+ * \param ar with a serialized EcdsaSignature at the beginning
+ * \param signature to deserialize
+ * \param public_key_algorithm to determine the size of the signature
+ * \return size of the deserialized EcdsaSignature
+ */
+size_t deserialize(InputArchive&, EcdsaSignature&, const PublicKeyAlgorithm&);
+
+/**
+ * \brief Deserializes a Signature from a binary archive
+ * \param ar with a serialized Signature at the beginning
+ * \param signature to deserialize
+ * \return size of the deserialized Signature
+ */
+size_t deserialize(InputArchive&, Signature&);
+
+/**
+ * Try to extract ECDSA signature from signature variant
+ * \param sig Signature variant (of some type)
+ * \return ECDSA signature (optionally)
+ */
+boost::optional<EcdsaSignature> extract_ecdsa_signature(const Signature& sig);
+
+} // namespace v2
+} // namespace security
+} // namespace vanetza
+
+#endif /* SIGNATURE_HPP_ZWPLNDVE */