Use arrays for finding sources

[aomerk]

Example protobuf response:

{
    "errors": [],
    "findings": [
        {
            "addresses": [],
            "labels": [],
            "relatedAlerts": [],
            "metadata": {},
            "indicators": {},
            "protocol": "ethereum",
            "severity": "LOW",
            "type": "INFORMATION",
            "alertId": "FORTA-1",
            "name": "Alert with chain source",
            "description": "Test Alert ",
            "private": false,
            "uniqueKey": "ali",
            "source": {
                "transactions": [],
                "blocks": [],
                "urls": [],
                "chains": [
                    {
                        "chainId": "999"
                    }
                ],
                "alerts": [],
                "customSources": []
            }
        }
    ],
    "metadata": {
        "timestamp": "2023-08-03T06:38:11.645Z"
    },
    "status": "SUCCESS",
    "timestamp": "",
    "latencyMs": 0,
    "private": false
}