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FLASHING.md says how to take a newer version of the colleague's tree (copy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

@@ -0,0 +1,77 @@
+#ifndef CONFIDENT_QUANTITY_HPP_B2XVJERI
+#define CONFIDENT_QUANTITY_HPP_B2XVJERI
+
+#include <limits>
+
+namespace vanetza
+{
+
+/**
+ * ConfidentQuantity combines a boost::quantity value with a confidence level.
+ *
+ * Usually, a confidence level of 95% is used in ITS specifications.
+ * If no confidence level is explicitly given a worst case value is used, i.e.
+ * the maximum value representable by the underlying type or infinity.
+ */
+template<typename T>
+class ConfidentQuantity
+{
+public:
+    constexpr T worst_confidence() const
+    {
+        using value_type = typename T::value_type;
+        return T::from_value(std::numeric_limits<value_type>::has_infinity ?
+            std::numeric_limits<value_type>::infinity() :
+            std::numeric_limits<value_type>::max());
+    }
+
+    constexpr T default_value() const
+    {
+        using value_type = typename T::value_type;
+        return T::from_value(std::numeric_limits<value_type>::has_quiet_NaN ?
+            std::numeric_limits<value_type>::quiet_NaN() : value_type());
+    }
+
+    constexpr bool is_nan(const T& t) const
+    {
+        return t.value() != t.value();
+    }
+
+    ConfidentQuantity() :
+        m_value(default_value()), m_confidence(worst_confidence()) {}
+    ConfidentQuantity(const T& value) :
+        m_value(value), m_confidence(worst_confidence()) {}
+    ConfidentQuantity(const T& value, const T& confidence) :
+        m_value(value), m_confidence(!is_nan(confidence) ? confidence : worst_confidence()) {}
+
+    ConfidentQuantity(const ConfidentQuantity&) = default;
+    ConfidentQuantity& operator=(const ConfidentQuantity&) = default;
+    ConfidentQuantity(ConfidentQuantity&&) = default;
+    ConfidentQuantity& operator=(ConfidentQuantity&&) = default;
+
+    void assign(const T& value, const T& confidence)
+    {
+        m_value = value;
+        m_confidence = !is_nan(confidence) ? confidence : worst_confidence();
+    }
+
+    const T& value() const
+    {
+        return m_value;
+    }
+
+    const T& confidence() const
+    {
+        return m_confidence;
+    }
+
+private:
+    T m_value;
+    T m_confidence;
+};
+
+
+} // namespace vanetza
+
+#endif /* CONFIDENT_QUANTITY_HPP_B2XVJERI */
+