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FLASHING.md says how to take a newer version of the colleague's tree (copy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

@@ -0,0 +1,40 @@
+#pragma once
+
+#include "certificate_storage.hpp"
+#include "credential_storage.hpp"
+#include "crl_store.hpp"
+#include "filesystem.hpp"
+#include "hashed_id8.hpp"
+#include "security_module.hpp"
+#include "station_config.hpp"
+#include "trust_list_storage.hpp"
+#include <memory>
+
+namespace vanetza
+{
+namespace pki
+{
+
+struct MainConfig
+{
+    std::filesystem::path config_path;
+    std::filesystem::path data_path;
+    std::string dc_url;
+    HashedId8 root_ca_hid8;
+    std::shared_ptr<StationConfiguration> station;
+    std::shared_ptr<SecurityModule> security;
+    std::shared_ptr<CertificateStorage> root_ca; // root CA certificates
+    std::shared_ptr<CertificateStorage> enrolment_credentials; // station's EC certificates
+    std::shared_ptr<CertificateStorage> tickets; // station's authorization tickets
+    std::shared_ptr<CertificateStorage> tlm; // trust list manager certificates
+    std::shared_ptr<CertificateStorage> authorization_authorities; // AA certs extracted from CTLs
+    std::shared_ptr<CertificateStorage> enrolment_authorities; // EA certs extracted from CTLs
+    std::shared_ptr<CredentialStorage> credentials; // private keys
+    std::shared_ptr<TrustListStorage> trust_lists;
+    std::shared_ptr<CrlFilesystemStore> crl_store; // certificate revocation lists
+};
+
+boost::optional<std::string> lookup_dc_url(const std::filesystem::path& ectl_file, const HashedId8& root_ca);
+
+} // namespace pki
+} // namespace vanetza