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FLASHING.md says how to take a newer version of the colleague's tree (copy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

@@ -0,0 +1,127 @@
+import os
+import re
+
+from conan import ConanFile
+from conan.errors import ConanException
+from conan.tools.cmake import CMake, CMakeToolchain, CMakeDeps, cmake_layout
+from conan.tools.scm import Git
+
+
+class VanetzaConan(ConanFile):
+    name = "vanetza"
+    url = "https://github.com/riebl/vanetza"
+    description = "Open-source implementation of the ETSI C-ITS protocol stack"
+    license = "LGPL-3.0-or-later"
+    package_type = "library"
+    languages = "C", "C++"
+    settings = "os", "compiler", "build_type", "arch"
+    options = {
+        "fPIC": [True, False],
+        "shared": [True, False],
+        "testing": [True, False],
+        "with_cryptopp": [True, False],
+        "with_openssl": [True, False],
+        "build_socktap": [True, False],
+        "build_certify": [True, False],
+        "build_benchmark": [True, False],
+    }
+    default_options = {
+        "fPIC": True,
+        "shared": False,
+        "testing": True,
+        "with_cryptopp": False,
+        "with_openssl": True,
+        "build_socktap": False,
+        "build_certify": False,
+        "build_benchmark": False,
+    }
+
+    def read_project_version(self) -> str | None:
+        version_re = re.compile(r"project\(Vanetza VERSION ([\d.]+)\)")
+        with open(os.path.join(self.recipe_folder, "CMakeLists.txt")) as f:
+            for line in f:
+                match = version_re.search(line)
+                if match:
+                    return match.group(1)
+        return None
+
+    def set_version(self):
+        project_version = self.read_project_version()
+        if not project_version:
+            raise ConanException("Could not read version from CMakeLists.txt")
+
+        git = Git(self)
+        try:
+            count = int(git.run(f"rev-list --count v{project_version}..HEAD"))
+            if count > 0:
+                short_hash = git.run("rev-parse --short HEAD")
+                self.version = f"{project_version}-dev+{count}.{short_hash}"
+        except Exception:
+            self.version = project_version
+
+    def config_options(self):
+        if self.settings.os == "Windows":
+            del self.options.fPIC
+
+    def configure(self):
+        if self.options.shared:
+            self.options.rm_safe("fPIC")
+
+    def layout(self):
+        cmake_layout(self)
+
+    def requirements(self):
+        self.requires("boost/[>=1.70]")
+        self.requires("geographiclib/[>=1.37]")
+        if self.options.with_cryptopp:
+            self.requires("cryptopp/[>=5.6.1]")
+        if self.options.with_openssl:
+            self.requires("openssl/[>=1.1 <4]")
+
+    def validate(self):
+        from conan.tools.build import check_min_cppstd
+
+        check_min_cppstd(self, "14")
+
+    def generate(self):
+        tc = CMakeToolchain(self)
+        tc.variables["BUILD_SHARED_LIBS"] = self.options.shared
+        tc.variables["BUILD_TESTS"] = self.options.testing
+        tc.variables["VANETZA_WITH_CRYPTOPP"] = self.options.with_cryptopp
+        tc.variables["VANETZA_WITH_OPENSSL"] = self.options.with_openssl
+        tc.variables["BUILD_SOCKTAP"] = self.options.build_socktap
+        tc.variables["BUILD_CERTIFY"] = self.options.build_certify
+        tc.variables["BUILD_BENCHMARK"] = self.options.build_benchmark
+        tc.generate()
+        deps = CMakeDeps(self)
+        deps.generate()
+
+    def build(self):
+        cmake = CMake(self)
+        cmake.configure()
+        cmake.build()
+        if self.options.testing:
+            cmake.test()
+
+    def package(self):
+        cmake = CMake(self)
+        cmake.install()
+
+    def package_info(self):
+        # ordered from dependents to dependencies for correct static linking
+        self.cpp_info.libs = [
+            "vanetza_facilities",
+            "vanetza_btp",
+            "vanetza_geonet",
+            "vanetza_security",
+            "vanetza_dcc",
+            "vanetza_access",
+            "vanetza_net",
+            "vanetza_gnss",
+            "vanetza_common",
+            "vanetza_asn1",
+            "vanetza_asn1_its",
+            "vanetza_asn1_pki",
+            "vanetza_asn1_security",
+            "vanetza_asn1_support",
+        ]