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FLASHING.md says how to take a newer version of the colleague's tree (copy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

@@ -0,0 +1,41 @@
+#ifndef INTERFACE_HPP_4SUUTA6X
+#define INTERFACE_HPP_4SUUTA6X
+
+#include <memory>
+
+namespace vanetza
+{
+
+// forward declarations
+class ChunkPacket;
+
+namespace dcc
+{
+
+// forward declarations
+struct DataRequest;
+
+/**
+ * DCC_access interface for data request from upper layers
+ */
+class RequestInterface
+{
+public:
+    virtual void request(const DataRequest&, std::unique_ptr<ChunkPacket>) = 0;
+    virtual ~RequestInterface() = default;
+};
+
+/**
+ * Null implemenation of DCC data request interface
+ */
+class NullRequestInterface : public RequestInterface
+{
+public:
+    void request(const DataRequest&, std::unique_ptr<ChunkPacket>) override {}
+};
+
+} // namespace dcc
+} // namespace vanetza
+
+#endif /* INTERFACE_HPP_4SUUTA6X */
+