Keep vanetza-idf in obu-firmware, so a plain clone builds the firmware

obu-firmware builds against the vanetza-idf C-ITS library, which until now
came from the colleague's microbu-esp32c5 tree beside the repository and was
not tracked here, so a clone of this repository could not build the firmware
it ships. The library alone is now part of obu-firmware, as
obu-firmware/external/vanetza-idf: their external/vanetza-idf at commit
cf4b99f, unchanged (9775 files; see its PROVENANCE.md). CMake takes it from
there by default; -DVANETZA_IDF_DIR still points the build elsewhere.

The rest of the colleague's tree (their own VAM firmware, PKI tooling,
station-link Python tools, the V2X2MAP bridge) stays out of this repository
and gitignored; nothing is pushed to their repository. NOTES.md, docs/06,
TODO.md and the pcap verifier's usage line point at the new location.

obu-firmware/external/vanetza-idf/tools/certify/utils.cpp

@@ -0,0 +1,35 @@
+#include "utils.hpp"
+#include <cstdint>
+#include <stdexcept>
+#include <sstream>
+
+void permission_string_to_buffer(const std::string& in, vanetza::ByteBuffer& out)
+{
+    if (in.size() / 8 != out.size() - 1 /* version */) {
+        std::stringstream ss;
+        ss << "Size mismatch, expected " << (out.size() - 1) << " bytes encoded with one bit per byte.";
+        throw std::runtime_error(ss.str());
+    }
+
+    uint8_t byte = 0;
+    int index = 0;
+
+    for (auto it = in.begin(); it < in.end(); ++it) {
+        byte <<= 1;
+
+        if (*it == '0') {
+            byte &= 0xFE; // clear last bit
+        } else if (*it == '1') {
+            byte |= 1; // set last bit
+        } else {
+            throw std::runtime_error("Unexpected character in permissions, expected only '0' and '1'.");
+        }
+
+        if ((index + 1) % 8 == 0) {
+            out.at(1 /* version */ + (index / 8)) = byte;
+            byte = 0;
+        }
+
+        ++index;
+    }
+}