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FLASHING.md says how to take a newer version of the colleague's tree (copy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

@@ -0,0 +1,62 @@
+#ifndef ECC_POINT_HPP_XCESTUEB
+#define ECC_POINT_HPP_XCESTUEB
+
+#include <vanetza/common/byte_buffer.hpp>
+#include <vanetza/security/ecc_point.hpp>
+#include <vanetza/security/v2/serialization.hpp>
+#include <cstdint>
+
+namespace vanetza
+{
+namespace security
+{
+namespace v2
+{
+
+/// forward declaration, see public_key.hpp
+enum class PublicKeyAlgorithm: uint8_t;
+
+/// EccPointType specified in TS 103 097 v1.2.1 in section 4.2.6
+enum class EccPointType : uint8_t
+{
+    X_Coordinate_Only = 0,
+    Compressed_Lsb_Y_0 = 2,
+    Compressed_Lsb_Y_1 = 3,
+    Uncompressed = 4
+};
+
+/**
+ * \brief Determines EccPointType to a given EccPoint
+ * \param ecc_point
+ * \return type
+ */
+EccPointType get_type(const EccPoint&);
+
+/**
+ * \brief Serializes an EccPoint into a binary archive
+ * \param ar to serialize in
+ * \param ecc_point to serialize
+ * \param pka Public key algorithm used for EccPoint
+ */
+void serialize(OutputArchive&, const EccPoint&, PublicKeyAlgorithm);
+
+/**
+ * \brief Deserializes an EccPoint from a binary archive
+ * \param ar with a serialized EccPoint at the beginning,
+ * \param ecc_point to deserialize
+ * \param pka to get field size of the encoded coordinates
+ */
+void deserialize(InputArchive&, EccPoint&, PublicKeyAlgorithm);
+
+/**
+ * \brief Calculates size of an EccPoint
+ * \param ecc_point
+ * \return size_t containing the number of octets needed to serialize the EccPoint
+ */
+size_t get_size(const EccPoint&);
+
+} // namespace v2
+} // namespace security
+} // namespace vanetza
+
+#endif /* ECC_POINT_HPP_XCESTUEB */