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/asn1/EN302637-3v131-DENM.asn

@@ -0,0 +1,109 @@
+DENM-PDU-Descriptions {
+ itu-t (0) identified-organization (4) etsi (0) itsDomain (5) wg1 (1) en (302637) denm (1) version (2)
+}
+
+DEFINITIONS AUTOMATIC TAGS ::=
+
+BEGIN
+
+IMPORTS
+ItsPduHeader, CauseCode, Speed, InformationQuality, ReferencePosition, ClosedLanes, DangerousGoodsExtended, Heading, LanePosition, LightBarSirenInUse, RoadType, HeightLonCarr, PosLonCarr, PosCentMass, PositioningSolutionType, RequestResponseIndication, StationType, SpeedLimit, StationarySince, TimestampIts, WheelBaseVehicle, TurningRadius, PosFrontAx, PositionOfOccupants, Temperature, VehicleMass, VehicleIdentification, EnergyStorageType, ActionID, ItineraryPath, NumberOfOccupants, PositionOfPillars, RelevanceTrafficDirection, RestrictedTypes, Traces, TransmissionInterval, ValidityDuration, RelevanceDistance, EventHistory, TrafficRule, DeltaReferencePosition FROM ITS-Container {
+itu-t (0) identified-organization (4) etsi (0) itsDomain (5) wg1 (1) ts (102894) cdd (2) version (2)
+};
+
+
+DENM ::= SEQUENCE {
+    header ItsPduHeader,
+    denm DecentralizedEnvironmentalNotificationMessage
+}
+
+DecentralizedEnvironmentalNotificationMessage ::= SEQUENCE {
+    management ManagementContainer,
+    situation SituationContainer OPTIONAL,
+    location LocationContainer OPTIONAL,
+    alacarte AlacarteContainer OPTIONAL
+}
+
+ManagementContainer ::= SEQUENCE {
+    actionID ActionID,
+    detectionTime TimestampIts,
+    referenceTime TimestampIts,
+    termination Termination OPTIONAL,
+    eventPosition ReferencePosition,
+    relevanceDistance RelevanceDistance OPTIONAL,
+    relevanceTrafficDirection RelevanceTrafficDirection OPTIONAL,
+    validityDuration ValidityDuration DEFAULT defaultValidity,
+    transmissionInterval TransmissionInterval OPTIONAL,
+    stationType StationType,
+    ...
+}
+
+SituationContainer ::= SEQUENCE {
+    informationQuality InformationQuality,
+    eventType CauseCode,
+    linkedCause CauseCode OPTIONAL,
+    eventHistory EventHistory OPTIONAL,
+    ...
+}
+
+LocationContainer ::= SEQUENCE {
+    eventSpeed Speed OPTIONAL,
+    eventPositionHeading Heading OPTIONAL,
+    traces Traces,
+    roadType RoadType OPTIONAL,
+    ...
+}
+
+ImpactReductionContainer ::= SEQUENCE {
+    heightLonCarrLeft HeightLonCarr,
+    heightLonCarrRight HeightLonCarr,
+    posLonCarrLeft PosLonCarr,
+    posLonCarrRight PosLonCarr,
+    positionOfPillars PositionOfPillars,
+    posCentMass PosCentMass,
+    wheelBaseVehicle WheelBaseVehicle,
+    turningRadius TurningRadius,
+    posFrontAx PosFrontAx,
+    positionOfOccupants PositionOfOccupants,
+    vehicleMass VehicleMass,
+    requestResponseIndication RequestResponseIndication
+}
+
+RoadWorksContainerExtended ::= SEQUENCE {
+    lightBarSirenInUse LightBarSirenInUse OPTIONAL,
+    closedLanes ClosedLanes OPTIONAL,
+    restriction RestrictedTypes OPTIONAL,
+    speedLimit SpeedLimit OPTIONAL,
+    incidentIndication CauseCode OPTIONAL,
+    recommendedPath ItineraryPath OPTIONAL,
+    startingPointSpeedLimit DeltaReferencePosition OPTIONAL,
+    trafficFlowRule TrafficRule OPTIONAL,
+    referenceDenms ReferenceDenms OPTIONAL
+ }
+
+StationaryVehicleContainer ::= SEQUENCE {
+    stationarySince StationarySince OPTIONAL,
+    stationaryCause CauseCode OPTIONAL,
+    carryingDangerousGoods DangerousGoodsExtended OPTIONAL,
+    numberOfOccupants NumberOfOccupants OPTIONAL,
+    vehicleIdentification VehicleIdentification OPTIONAL,
+    energyStorageType EnergyStorageType OPTIONAL
+}
+
+AlacarteContainer ::= SEQUENCE {
+    lanePosition LanePosition OPTIONAL,
+    impactReduction ImpactReductionContainer OPTIONAL,
+    externalTemperature Temperature OPTIONAL,
+    roadWorks RoadWorksContainerExtended OPTIONAL,
+    positioningSolution PositioningSolutionType OPTIONAL,
+    stationaryVehicle StationaryVehicleContainer OPTIONAL,
+    ...
+}
+
+defaultValidity INTEGER ::= 600
+
+Termination ::= ENUMERATED {isCancellation(0), isNegation (1)}
+
+ReferenceDenms ::= SEQUENCE (SIZE(1..8, ...)) OF ActionID
+
+END