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FLASHING.md says how to take a newer version of the colleague's tree (copy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

@@ -0,0 +1,85 @@
+#ifndef FACTORY_HPP_QLKNHPWZ
+#define FACTORY_HPP_QLKNHPWZ
+
+#include <functional>
+#include <map>
+#include <memory>
+#include <utility>
+
+namespace vanetza
+{
+
+/**
+ * Factory for a group of classes implementing T
+ */
+template<typename T, typename... Args>
+class Factory
+{
+public:
+    using Result = std::unique_ptr<T>;
+    using Function = std::function<Result(Args...)>;
+
+    Factory() : m_default(m_functions.end())
+    {
+    }
+
+    /**
+     * Create an instance of T using a named implementation
+     * \param name of wanted implementation
+     * \return created instance or nullptr if not found
+     */
+    Result create(const std::string& name, Args... args) const
+    {
+        std::unique_ptr<T> obj;
+        auto found = m_functions.find(name);
+        if (found != m_functions.end()) {
+            obj = found->second(std::forward<Args>(args)...);
+        }
+        return obj;
+    }
+
+    /**
+     * Create object using default implementation
+     * \return created instance or nullptr if no default is configured
+     */
+    Result create(Args... args) const
+    {
+        std::unique_ptr<T> obj;
+        if (m_default != m_functions.end()) {
+            obj = m_default->second(std::forward<Args>(args)...);
+        }
+        return obj;
+    }
+
+    /**
+     * Add an implementation to factory
+     * \param name of implementation
+     * \param f function creating a new instance of this implementation
+     * \return true if added successfully, i.e. no previous addition with same name
+     */
+    bool add(const std::string& name, Function f)
+    {
+        return m_functions.emplace(name, std::move(f)).second;
+    }
+
+    /**
+     * Set default implementation
+     * \param name selected default implementation
+     * \return true if an implementation exists with selected name
+     */
+    bool configure_default(const std::string& name)
+    {
+        m_default = m_functions.find(name);
+        return m_default != m_functions.end();
+    }
+
+private:
+    using map_type = std::map<std::string, Function>;
+    map_type m_functions;
+    typename map_type::const_iterator m_default;
+};
+
+} // namespace vanetza
+
+#endif /* FACTORY_HPP_QLKNHPWZ */
+