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FLASHING.md says how to take a newer version of the colleague's tree (copy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

@@ -0,0 +1,110 @@
+#ifndef NAIVE_CERTIFICATE_PROVIDER_HPP_MTULFLKX
+#define NAIVE_CERTIFICATE_PROVIDER_HPP_MTULFLKX
+
+#include <memory>
+#include <string>
+#include <vanetza/common/runtime.hpp>
+#include <vanetza/security/backend.hpp>
+#include <vanetza/security/v2/certificate.hpp>
+#include <vanetza/security/v2/certificate_provider.hpp>
+
+namespace vanetza
+{
+namespace security
+{
+namespace v2
+{
+
+/**
+ * \brief A very simplistic certificate provider
+ *
+ * This certificate provider signs its certificates with a randomly generated root certificate. This means the
+ * signatures produced based on this certificate provider can't be verified by other parties.
+ *
+ * It's intended for experimenting with secured messages without validating signatures.
+ */
+class NaiveCertificateProvider : public CertificateProvider
+{
+public:
+    NaiveCertificateProvider(const Runtime&);
+
+    /**
+     * \brief get own certificate for signing
+     * \return own certificate
+     */
+    const Certificate& own_certificate() override;
+
+    /**
+     * Get own certificate chain, excluding the leaf certificate and root CA
+     * \return own certificate chain
+     */
+    std::list<Certificate> own_chain() override;
+
+    /**
+     * \brief get own private key
+     * \return private key
+     */
+    const ecdsa256::PrivateKey& own_private_key() override;
+
+    /**
+     * \brief get ticket signer certificate (same for all instances)
+     * \return signing authorization authority certificate
+     */
+    const Certificate& aa_certificate();
+
+    /**
+     * \brief get root certificate (same for all instances)
+     * \return signing root certificate
+     */
+    const Certificate& root_certificate();
+
+    /**
+     * \brief generate an authorization ticket
+     * \return generated certificate
+     */
+    Certificate generate_authorization_ticket();
+
+    /**
+     * \brief sign an authorization ticket
+     * \param certificate certificate to sign
+     */
+    void sign_authorization_ticket(Certificate& certificate);
+
+private:
+    /**
+     * \brief get root key (same for all instances)
+     * \return root key
+     */
+    const ecdsa256::KeyPair& aa_key_pair();
+
+    /**
+     * \brief get root key (same for all instances)
+     * \return root key
+     */
+    const ecdsa256::KeyPair& root_key_pair();
+
+    /**
+     * \brief generate a authorization authority certificate
+     *
+     * \return generated certificate
+     */
+    Certificate generate_aa_certificate(const std::string& subject_name);
+
+    /**
+     * \brief generate a root certificate
+     *
+     * \return generated certificate
+     */
+    Certificate generate_root_certificate(const std::string& subject_name);
+
+    std::unique_ptr<Backend> m_crypto_backend;
+    const Runtime& m_runtime;
+    const ecdsa256::KeyPair m_own_key_pair;
+    Certificate m_own_certificate;
+};
+
+} // namespace v2
+} // namespace security
+} // namespace vanetza
+
+#endif /* NAIVE_CERTIFICATE_PROVIDER_HPP_MTULFLKX */