External_writer_add

To add an external writer to MistServer you will need to pass a name, cmdline and protocols

{
    "external_writer_add": {
        "name": "example",               /// name for the external writer
        "cmdline": "example",           /// command to run as in bash or url
        "protocols": [                 /// protocols that will trigger the external writer to be used
            "test",                    
            "test2",
            "test3"
        ]
    }
}

The response will contain the updated external_writer_list