[caddy] Handle reverse proxy errors

[LaurenceJJones]

When caddy receives no response from upstream server it logs a JSON line such as

{
  "level": "error",
  "ts": 1712066552.3486984,
  "logger": "http.handlers.reverse_proxy",
  "msg": "aborting with incomplete response",
  "upstream": "172.19.0.8:3000",
  "duration": 0.00405423,
  "request": {
    "remote_ip": "x.x.x.x",
    "remote_port": "56973",
    "client_ip": "x.x.x.x",
    "proto": "HTTP/2.0",
    "method": "GET",
    "host": "git.mydomain.com",
    "uri": "/user/events",
    "headers": {
      "Cache-Control": [
        "no-cache"
      ],
      "Cookie": [],
      "Sec-Fetch-Dest": [
        "empty"
      ],
      "Te": [
        "trailers"
      ],
      "Pragma": [
        "no-cache"
      ],
      "X-Forwarded-Proto": [
        "https"
      ],
      "User-Agent": [
        "Mozilla/5.0 (Windows NT 10.0; Win64; x64; rv:123.0) Gecko/20100101 Firefox/123.0"
      ],
      "X-Forwarded-Host": [
        "git.mydomain.com"
      ],
      "Accept-Encoding": [
        "gzip, deflate, br"
      ],
      "Sec-Fetch-Mode": [
        "cors"
      ],
      "Accept": [
        "text/event-stream"
      ],
      "Accept-Language": [
        "de,en-US;q=0.7,en;q=0.3"
      ],
      "Sec-Fetch-Site": [
        "same-origin"
      ],
      "X-Forwarded-For": [
        "x.x.x.x"
      ]
    },
    "tls": {
      "resumed": false,
      "version": 772,
      "cipher_suite": 4865,
      "proto": "h2",
      "server_name": "git.mydomain.com"
    }
  },
  "error": "reading: context canceled"
}

Currently the parser is not set to handle these lines as it will attempt to grab certain variables from the JSON log line. This will cause warning to be logged to the crowdsec log file, however, this will not impact performance or the impact for CrowdSec to do its job. Its purely just adds alot of warnings.