Add linked station

[tigroo]

No test, we provide a new optional field linked station id.

[ymorin-orange]

This is a minor, backward compatible evolution, so the minor version should be updated, not the patchlevel, so it should be 2.4.0.

[ymorin-orange]

I think it would be better is that were an array rather than a single object. Indeed, there are tractors that may have two (or more!) trailers; for example

Also, for platooning, there might be a bunch of following trucks, so the head of the platoon would need to link to all the trucks that follows it (and individual trucks may also want to link to their own followers.

Do we also want to identify the type of link: following or leading?

{
  "linked_station_ids": {
    "type": "array",
    "description": "list of following or leading stations IDs",
    "minItems": 1,
    "items": {
      "type": "object",
      "description": "Linked station",
      "required": ["station_id"],
      "properties": {
        "station_id": {
          "type": "integer",
          "description": "Identifier for a linked ITS-S, as a trailer or a platooning pair.",
          "minimum": 0,
          "maximum": 4294967295,
          "examples": [
            4294967295,
            42
          ]
        },
        "relation": {
          "type": "string",
          "description": "how the linked station relates to this one",
          "enum": [
            "trailer",
            "tractor",
            "platoon"
          ]
        },
        "order": {
          "type": "string",
          "description": "whether the linked station trails or leads this one",
          "enum": [
            "trails",
            "leads",
          ]
        }
      }
    }
  }
}

[ymorin-orange]

• change the version to 2.4.0
• maybe extend the schema to allow for more flexibility in the relationship description, as suggested in the comment