Keep vanetza-idf in obu-firmware, so a plain clone builds the firmware

obu-firmware builds against the vanetza-idf C-ITS library, which until now
came from the colleague's microbu-esp32c5 tree beside the repository and was
not tracked here, so a clone of this repository could not build the firmware
it ships. The library alone is now part of obu-firmware, as
obu-firmware/external/vanetza-idf: their external/vanetza-idf at commit
cf4b99f, unchanged (9775 files; see its PROVENANCE.md). CMake takes it from
there by default; -DVANETZA_IDF_DIR still points the build elsewhere.

The rest of the colleague's tree (their own VAM firmware, PKI tooling,
station-link Python tools, the V2X2MAP bridge) stays out of this repository
and gitignored; nothing is pushed to their repository. NOTES.md, docs/06,
TODO.md and the pcap verifier's usage line point at the new location.

obu-firmware/external/vanetza-idf/vanetza/security/v3/static_certificate_provider.hpp

@@ -0,0 +1,47 @@
+#pragma once
+#include <vanetza/security/v3/certificate_provider.hpp>
+#include <vanetza/security/v3/persistence.hpp>
+
+namespace vanetza
+{
+namespace security
+{
+namespace v3
+{
+
+/**
+ * \brief A simple certificate provider
+ *
+ * This certificate provider uses a static certificate and key pair that is pre-generated.
+ */
+class StaticCertificateProvider : public BaseCertificateProvider
+{
+public:
+    /**
+     * Create static certificate provider with empty chain
+     * \param authorization_ticket
+     * \param ticket_key private key of given authorization ticket
+     */
+    StaticCertificateProvider(const Certificate& authorization_ticket, const PrivateKey& ticket_key);
+
+    /**
+     * Get own certificate to use for signing
+     * \return own certificate
+     */
+    virtual const Certificate& own_certificate() override;
+
+    /**
+     * Get private key associated with own certificate
+     * \return private key
+     */
+    virtual const PrivateKey& own_private_key() override;
+
+private:
+    Certificate authorization_ticket;
+    PrivateKey authorization_ticket_key;
+    std::list<Certificate> chain;
+};
+
+} // namespace v3
+} // namespace security
+} // namespace vanetza