Trigger Editor: known_value field is not sent to Astarte when installing "incoming data" triggers

[davidebriani]

When defining an "incoming data" trigger with a comparison on an interface value, the known_value is not sent to Astarte when installing the trigger: Astarte returns an HTTP 422 error and the installation fails.

For example:

{
    "name": "sample-trigger",
    "action": {
        "http_url": "https://domain.com",
        "http_method": "post",
        "http_static_headers": {}
    },
    "simple_triggers": [
        {
            "type": "data_trigger",
            "on": "incoming_data",
            "interface_name": "some.astarte.Interface",
            "interface_major": 0,
            "match_path": "/mypath",
            "value_match_operator": ">",
            "known_value": 1
        }
    ]
}

[davidebriani]

Closing as duplicate of #393 and already fixed by #402 for Astarte Dashboard v1.1.2 development branch.