Steps to reproduce:

1. Perform "maintenance.get" API request with body:

 {
    "jsonrpc": "2.0",
    "method": "maintenance.get",
    "params": {
        "hostids": 12345
    },
    "id": 2,
    "auth": "<API key>"
}

Result:
HTTP/1.1 500 Internal Server Error
Expected:
Return maintenance periods containing host ID "12345"

The maintenance.get documentation states that the parameter must be submitted as "ID/array". The request works if the single ID is sent as an array instead. The same API request worked as expected in Zabbix 6.4.17 when not sent as an array. I can't see any changes to "maintenance.get" in API changes for 7.0.