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FLASHING.md says how to take a newer version of the colleague's tree (copy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

@@ -0,0 +1,31 @@
+#pragma once
+
+#include <vanetza/asn1/asn1c_wrapper.hpp>
+#include <vanetza/asn1/security/EtsiTs103097Data-Signed.h>
+#include <vanetza/asn1/security/Ieee1609Dot2Data.h>
+
+namespace vanetza
+{
+namespace pki
+{
+
+class SignedData : public asn1::asn1c_oer_wrapper<Vanetza_Security_EtsiTs103097Data_Signed_55P0_t>
+{
+public:
+    using wrapper = asn1::asn1c_oer_wrapper<Vanetza_Security_EtsiTs103097Data_Signed_55P0_t>;
+
+    SignedData() : wrapper(asn_DEF_Vanetza_Security_EtsiTs103097Data_Signed_55P0)
+    {
+    }
+
+    /**
+     * Graft the envelope into a parent that takes over ownership.
+     * Consuming: only callable on an rvalue, leaving the source empty.
+     *
+     * \param dest Ieee1609Dot2Data field of the parent to move the envelope into
+     */
+    void move_into(Vanetza_Security_Ieee1609Dot2Data_t& dest) &&;
+};
+
+} // namespace pki
+} // namespace vanetza