Serialization of cookie query for Expires attributes with hurlfmt

[jcamiel]

When exporting an Hurl file containing a cookie query with Expires attributes, the serialized attribute is Expire:

GET http://localhost

HTTP/1.1 200
[Asserts]
cookie "Session[Expires]" exists

$ hurlfmt --format json /tmp/test.hurl

{
  "entries": [
    {
      "request": {
        "method": "GET",
        "url": "http://localhost"
      },
      "response": {
        "version": "HTTP/1.1",
        "status": 200,
        "asserts": [
          {
            "query": {
              "type": "cookie",
              "expr": "Session[Expire]"
            },
            "predicate": {
              "type": "exist"
            }
          }
        ]
      }
    }
  ]
}

[fabricereix]

fix in #101