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FLASHING.md says how to take a newer version of the colleague's tree (copy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/socktap/nfiniity_cube_radio.proto

@@ -0,0 +1,79 @@
+syntax = "proto2";
+
+message CommandRequest {
+  oneof kind {
+    LifecycleAction lifecycle = 1;
+    LinkLayerTransmission linklayer_tx = 2;
+    RadioConfiguration radio_cfg = 3;
+  }
+}
+
+message CommandResponse {
+  enum Status {
+    SUCCESS = 0;
+    FAILURE = 1;
+    UNKNOWN = 2;
+    NOT_IMPLEMENTED = 3;
+  }
+
+  required Status status = 1;
+  optional string message = 2;
+  optional CommandResponseData data = 3;
+}
+
+message CommandResponseData {
+  oneof kind {
+     RadioConfiguration radio_cfg = 1;
+  }
+}
+
+enum LifecycleAction {
+  SOFT_RESET = 0;
+  HARD_RESET = 1;
+}
+
+enum LinkLayerPriority {
+  BACKGROUND = 0;
+  BEST_EFFORT = 1;
+  VIDEO = 2;
+  VOICE = 3;
+}
+
+message RadioConfiguration {
+  optional bytes address = 1;
+  optional uint32 channel_frequency_mhz = 2;
+  optional bool filter_unicast_destination = 3;
+  optional sint32 default_tx_power_cbm = 4;
+  optional uint32 default_tx_datarate_500kbps = 5;
+}
+
+message LinkLayerTransmission {
+  optional bytes source = 1;
+  required bytes destination = 2;
+  required LinkLayerPriority priority = 3;
+  optional uint32 channel = 4;
+  optional uint32 datarate_500kbps = 5;
+  optional sint32 power_cbm = 6; // centi Bel mW = 10 * dBm
+  required bytes payload = 10;
+}
+
+message LinkLayerReception {
+  required bytes source = 1;
+  required bytes destination = 2;
+  optional uint32 channel = 4;
+  optional sint32 power_cbm = 6;
+  required bytes payload = 10;
+}
+
+message ChannelBusyRatio {
+  required uint32 busy = 1;
+  required uint32 total = 2;
+}
+
+message GossipMessage {
+  oneof kind {
+    ChannelBusyRatio cbr = 1;
+    LinkLayerReception linklayer_rx = 2;
+  }
+}
+