Return [object Object] if field is array

Hello.

When I try to add field with type array, I see list of [object Object],[object Object] ...

For example. I have stacktrace which in elasticsearch looks like

....
"exception": {
    "frames": [
        {
            "method": "invokeInOurTx",
            "line": 22,
            "class": "org.jboss.as.ejb3"
        },
        {
            "method": "invokeInOurTx",
            "line": 22,
            "class": "org.jboss.as.ejb3"
        },
        {
            "method": "invokeInOurTx",
            "line": 22,
            "class": "org.jboss.as.ejb3"
        },
       ...
    ]
},
...

and in logtrail.json I set "message_format": {{exception.frames}}. The result will be next: [object Object],[object Object],[object Object]

I understand that this is the expected result. [{a: "a"},{b: "b"}].toString() => [object Object],[object Object]. But it would be great if there was an opportunity to map values and return as raw str.

sivasamyk / logtrail

Return [object Object] if field is array #394