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FLASHING.md says how to take a newer version of the colleague's tree (copy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/security/v2/validity_restriction.hpp

@@ -0,0 +1,179 @@
+#ifndef VALIDITY_RESTRICTION_HPP_LMCUHYLJ
+#define VALIDITY_RESTRICTION_HPP_LMCUHYLJ
+
+#include <vanetza/common/bit_number.hpp>
+#include <vanetza/security/v2/region.hpp>
+#include <vanetza/security/v2/serialization.hpp>
+#include <boost/variant/variant.hpp>
+#include <chrono>
+
+namespace vanetza
+{
+namespace security
+{
+namespace v2
+{
+
+using Time32 = uint32_t;
+using Time64 = uint64_t;
+
+class Duration
+{
+public:
+    enum class Units
+    {
+        Seconds = 0x0,
+        Minutes = 0x1,
+        Hours = 0x2,
+        Sixty_Hour_Blocks = 0x3,
+        Years = 0x4
+    };
+
+    Duration();
+    Duration(BitNumber<uint16_t, 13> value, Units unit);
+    Duration(uint16_t raw);
+
+    uint16_t raw() const
+    {
+        return m_raw;
+    }
+
+    /**
+     * Get duration's unit.
+     * \return unit part of raw value
+     */
+    Units unit() const
+    {
+        return static_cast<Units>(m_raw >> 13);
+    }
+
+    /**
+     * Get duration's ticks value
+     * \return value part of raw value
+     */
+    uint16_t value() const
+    {
+        return m_raw & 0x1FFF; // mask upper 3 bit
+    }
+
+    /**
+     * Convert duration to seconds.
+     * \note std::chrono::seconds is wide enough to represent 2^13 years
+     * \return duration in seconds
+     */
+    std::chrono::seconds to_seconds() const;
+
+private:
+    uint16_t m_raw;
+};
+
+size_t get_size(const Duration&);
+
+enum class ValidityRestrictionType : uint8_t
+{
+    Time_End = 0,                   // end_validity
+    Time_Start_And_End = 1,         // start_and_end_valididty
+    Time_Start_And_Duration = 2,    // start_and_duration_validity
+    Region = 3                      // GeographicRegion
+};
+
+struct StartAndEndValidity
+{
+    StartAndEndValidity() = default;
+    StartAndEndValidity(Time32 start, Time32 end);
+
+    Time32 start_validity;
+    Time32 end_validity;
+};
+
+struct StartAndDurationValidity
+{
+    StartAndDurationValidity() = default;
+    StartAndDurationValidity(Time32 start, Duration);
+
+    Time32 start_validity;
+    Duration duration;
+};
+
+using EndValidity = Time32;
+
+typedef boost::variant<EndValidity, StartAndEndValidity, StartAndDurationValidity, GeographicRegion> ValidityRestriction;
+
+/**
+ * Determines ValidityRestrictionType to a given ValidityRestriction
+ * \param ValidityRestriction
+ */
+ValidityRestrictionType get_type(const ValidityRestriction&);
+
+/**
+ * Calculates size of an object
+ * \param Object
+ * \return size_t containing the number of octets needed to serialize the object
+ */
+size_t get_size(const StartAndEndValidity&);
+size_t get_size(const StartAndDurationValidity&);
+size_t get_size(const ValidityRestriction&);
+size_t get_size(const Time32&);
+size_t get_size(const Time64&);
+size_t get_size(const Duration&);
+
+/**
+ * Deserializes a ValidityRestriction list from a binary archive
+ * \param archive with a serialized ValidityRestriction list at the beginning
+ * \param ValidityRestriction list to deserialize
+ * \return size of the ValidityRestriction list
+ */
+size_t deserialize(InputArchive&, ValidityRestriction&);
+
+/**
+ * Serializes a ValidityRestriction list into a binary archive
+ * \param archive to serialize in
+ * \param ValidityRestriction list to serialize
+ */
+void serialize(OutputArchive&, const ValidityRestriction&);
+
+namespace detail
+{
+
+template<ValidityRestrictionType>
+struct validity_restriction_type;
+
+template<>
+struct validity_restriction_type<ValidityRestrictionType::Time_End>
+{
+    using type = EndValidity;
+};
+
+template<>
+struct validity_restriction_type<ValidityRestrictionType::Time_Start_And_End>
+{
+    using type = StartAndEndValidity;
+};
+
+template<>
+struct validity_restriction_type<ValidityRestrictionType::Time_Start_And_Duration>
+{
+    using type = StartAndDurationValidity;
+};
+
+template<>
+struct validity_restriction_type<ValidityRestrictionType::Region>
+{
+    using type = GeographicRegion;
+};
+
+} // namespace details
+
+/**
+ * \brief resolve type for matching ValidityRestrictionType
+ *
+ * This is kind of the reverse function of get_type(const ValidityRestrictionType&)
+ */
+template<ValidityRestrictionType T>
+using validity_restriction_type = typename detail::validity_restriction_type<T>::type;
+
+} // namespace v2
+} // namespace security
+} // namespace vanetza
+
+#endif /* VALIDITY_RESTRICTION_HPP_LMCUHYLJ */