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FLASHING.md says how to take a newer version of the colleague's tree (copy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

@@ -0,0 +1,39 @@
+#ifndef DATA_INDICATION_HPP_5YZM172D
+#define DATA_INDICATION_HPP_5YZM172D
+
+#include <vanetza/btp/header.hpp>
+#include <vanetza/geonet/address.hpp>
+#include <vanetza/geonet/areas.hpp>
+#include <vanetza/geonet/data_indication.hpp>
+#include <vanetza/geonet/lifetime.hpp>
+#include <vanetza/geonet/position_vector.hpp>
+#include <vanetza/geonet/traffic_class.hpp>
+#include <boost/optional.hpp>
+#include <boost/variant.hpp>
+
+namespace vanetza
+{
+namespace btp
+{
+
+struct DataIndication
+{
+    DataIndication();
+    DataIndication(const geonet::DataIndication&, const HeaderA&);
+    DataIndication(const geonet::DataIndication&, const HeaderB&);
+
+    boost::optional<port_type> source_port;
+    port_type destination_port;
+    boost::optional<decltype(HeaderB::destination_port_info)> destination_port_info;
+    decltype(geonet::DataIndication::destination) destination;
+    decltype(geonet::DataIndication::its_aid) its_aid;
+    decltype(geonet::DataIndication::permissions) permissions;
+    geonet::ShortPositionVector source_position;
+    geonet::TrafficClass traffic_class;
+    boost::optional<geonet::Lifetime> remaining_packet_lifetime;
+};
+
+} // namespace btp
+} // namespace vanetza
+
+#endif /* DATA_INDICATION_HPP_5YZM172D */