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FLASHING.md says how to take a newer version of the colleague's tree (copy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/geonet/tests/timestamp.cpp

@@ -0,0 +1,101 @@
+#include <gtest/gtest.h>
+#include <vanetza/geonet/timestamp.hpp>
+#include <limits>
+
+using namespace vanetza::geonet;
+const Timestamp::absolute_unit_type abs_ms;
+const auto max = std::numeric_limits<Timestamp::value_type>::max();
+
+TEST(Timestamp, ctor) {
+    Timestamp a;
+    EXPECT_EQ(a.raw(), 0);
+
+    Timestamp b(Timestamp::time_type::from_value(832));
+    EXPECT_EQ(b.raw(), 832);
+
+    boost::posix_time::ptime p =
+        boost::posix_time::time_from_string("2004-01-01 00:00:00.000");
+    Timestamp c(p);
+    EXPECT_EQ(c.raw(), 0);
+
+    boost::posix_time::ptime q = p + boost::posix_time::milliseconds(5234);
+    Timestamp d(q);
+    EXPECT_EQ(d.raw(), 5234);
+}
+
+TEST(Timestamp, equality) {
+    Timestamp a(413 * abs_ms);
+    Timestamp b(412 * abs_ms);
+    EXPECT_NE(a, b);
+
+    Timestamp c(a);
+    EXPECT_EQ(a, c);
+}
+
+TEST(Timestamp, max) {
+    Timestamp a(895723 * abs_ms);
+    Timestamp b((895723 + max + 1) * abs_ms);
+    EXPECT_EQ(a, b);
+}
+
+TEST(Timestamp, is_greater) {
+    Timestamp a(238 * abs_ms);
+    Timestamp b(513 * abs_ms);
+    EXPECT_TRUE(is_greater(b, a));
+    EXPECT_FALSE(is_greater(a, b));
+
+    Timestamp c((513 + max / 2) * abs_ms);
+    EXPECT_TRUE(is_greater(c, b));
+    Timestamp d((514 + max / 2) * abs_ms);
+    EXPECT_FALSE(is_greater(d, b));
+
+    Timestamp e(Timestamp::time_type::from_value(max));
+    EXPECT_FALSE(is_greater(e, a));
+    Timestamp f(Timestamp::time_type::from_value(max/2));
+    EXPECT_FALSE(is_greater(e, f));
+    Timestamp g(Timestamp::time_type::from_value(max/2 + 1));
+    EXPECT_TRUE(is_greater(e, g));
+
+    Timestamp h(513 * abs_ms);
+    EXPECT_EQ(b, h);
+    EXPECT_FALSE(is_greater(b, h));
+}
+
+TEST(Timestamp, less) {
+    // operator< uses is_greater: we don't have to test a lot of combinations here
+    Timestamp a(582 * abs_ms);
+    Timestamp b(54884 * abs_ms);
+    EXPECT_LT(a, b);
+    Timestamp c(54884 * abs_ms);
+    EXPECT_FALSE(c < b);
+}
+
+TEST(Timestamp, addition) {
+    Timestamp a(89 * abs_ms);
+    a += 348 * Timestamp::millisecond();
+    EXPECT_EQ(a.raw(), 437);
+
+    Timestamp b = a + 3483 * Timestamp::millisecond();
+    EXPECT_EQ(a.raw(), 437);
+    EXPECT_EQ(b.raw(), 3920);
+}
+
+TEST(Timestamp, substraction) {
+    Timestamp a(3483 * abs_ms);
+    a -= 89 * Timestamp::millisecond();
+    EXPECT_EQ(a.raw(), 3394);
+    a -= 5000 * Timestamp::millisecond();
+    EXPECT_EQ(a.raw(), 4294965690);
+
+    Timestamp b = a - 23 * Timestamp::millisecond();
+    EXPECT_EQ(a.raw(), 4294965690);
+    EXPECT_EQ(b.raw(), 4294965667);
+}
+
+TEST(Timestamp, difference) {
+    Timestamp a(329 * abs_ms);
+    Timestamp b(394 * abs_ms);
+    EXPECT_EQ((a - b).value(), 4294967231);
+    EXPECT_EQ((b - a).value(), 65);
+}
+