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FLASHING.md says how to take a newer version of the colleague's tree (copy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/tools/pki/response_codes.cpp

@@ -0,0 +1,106 @@
+#include "response_codes.hpp"
+#include <string>
+
+namespace vanetza
+{
+namespace pki
+{
+
+std::string to_string(EnrolmentResponseCode code)
+{
+    switch (code.value) {
+        case Vanetza_Security_EnrolmentResponseCode_ok:
+            return "ok";
+        case Vanetza_Security_EnrolmentResponseCode_badcontenttype:
+            return "bad content type";
+        case Vanetza_Security_EnrolmentResponseCode_baditsstatus:
+            return "bad ITS status";
+        case Vanetza_Security_EnrolmentResponseCode_cantparse:
+            return "cannot parse";
+        case Vanetza_Security_EnrolmentResponseCode_decryptionfailed:
+            return "decryption failed";
+        case Vanetza_Security_EnrolmentResponseCode_deniedpermissions:
+            return "denied permissions";
+        case Vanetza_Security_EnrolmentResponseCode_deniedrequest:
+            return "denied request";
+        case Vanetza_Security_EnrolmentResponseCode_imnottherecipient:
+            return "I am not the recipient";
+        case Vanetza_Security_EnrolmentResponseCode_invalidencryptionkey:
+            return "invalid encryption key";
+        case Vanetza_Security_EnrolmentResponseCode_invalidkeys:
+            return "invalid keys";
+        case Vanetza_Security_EnrolmentResponseCode_invalidsignature:
+            return "invalid signature";
+        case Vanetza_Security_EnrolmentResponseCode_unknownencryptionalgorithm:
+            return "unknown encryption algorithm";
+        case Vanetza_Security_EnrolmentResponseCode_unknownits:
+            return "unknown ITS";
+        default:
+            return "unknown";
+    }
+}
+
+std::string to_string(AuthorizationResponseCode code)
+{
+    switch (code.value) {
+        case Vanetza_Security_AuthorizationResponseCode_ok:
+            return "ok";
+        case Vanetza_Security_AuthorizationResponseCode_its_aa_cantparse:
+            return "its-aa: cannot parse";
+        case Vanetza_Security_AuthorizationResponseCode_its_aa_badcontenttype:
+            return "its-aa: bad content type";
+        case Vanetza_Security_AuthorizationResponseCode_its_aa_imnottherecipient:
+            return "its-aa: not the recipient";
+        case Vanetza_Security_AuthorizationResponseCode_its_aa_unknownencryptionalgorithm:
+            return "its-aa: unknown encryption algorithm";
+        case Vanetza_Security_AuthorizationResponseCode_its_aa_decryptionfailed:
+            return "its-aa: decryption failed";
+        case Vanetza_Security_AuthorizationResponseCode_its_aa_keysdontmatch:
+            return "its-aa: keys don't match";
+        case Vanetza_Security_AuthorizationResponseCode_its_aa_incompleterequest:
+            return "its-aa: incomplete request";
+        case Vanetza_Security_AuthorizationResponseCode_its_aa_invalidencryptionkey:
+            return "its-aa: invalid encryption key";
+        case Vanetza_Security_AuthorizationResponseCode_its_aa_outofsyncrequest:
+            return "its-aa: out-of-sync request";
+        case Vanetza_Security_AuthorizationResponseCode_its_aa_unknownea:
+            return "its-aa: unknown EA";
+        case Vanetza_Security_AuthorizationResponseCode_its_aa_invalidea:
+            return "its-aa: invalid EA";
+        case Vanetza_Security_AuthorizationResponseCode_its_aa_deniedpermissions:
+            return "its-aa: denied permissions";
+        case Vanetza_Security_AuthorizationResponseCode_aa_ea_cantreachea:
+            return "aa-ea: cannot reach EA";
+        case Vanetza_Security_AuthorizationResponseCode_ea_aa_cantparse:
+            return "ea-aa: cannot parse";
+        case Vanetza_Security_AuthorizationResponseCode_ea_aa_badcontenttype:
+            return "ea-aa: bad content type";
+        case Vanetza_Security_AuthorizationResponseCode_ea_aa_imnottherecipient:
+            return "ea-aa: not the recipient";
+        case Vanetza_Security_AuthorizationResponseCode_ea_aa_unknownencryptionalgorithm:
+            return "ea-aa: unknown encryption algorithm";
+        case Vanetza_Security_AuthorizationResponseCode_ea_aa_decryptionfailed:
+            return "ea-aa: decryption failed";
+        case Vanetza_Security_AuthorizationResponseCode_invalidaa:
+            return "invalid AA";
+        case Vanetza_Security_AuthorizationResponseCode_invalidaasignature:
+            return "invalid AA signature";
+        case Vanetza_Security_AuthorizationResponseCode_wrongea:
+            return "wrong EA";
+        case Vanetza_Security_AuthorizationResponseCode_unknownits:
+            return "unknown ITS";
+        case Vanetza_Security_AuthorizationResponseCode_invalidsignature:
+            return "invalid signature";
+        case Vanetza_Security_AuthorizationResponseCode_invalidencryptionkey:
+            return "invalid encryption key";
+        case Vanetza_Security_AuthorizationResponseCode_deniedpermissions:
+            return "denied permissions";
+        case Vanetza_Security_AuthorizationResponseCode_deniedtoomanycerts:
+            return "denied: too many certificates";
+        default:
+            return "unknown(" + std::to_string(static_cast<long>(code.value)) + ")";
+    }
+}
+
+} // namespace pki
+} // namespace vanetza