Provide a set of ready to use interfaces

[bettio]

Astarte should provide a set of ready to install and user interfaces that can be used as an example and can be without further effort:

{
    "interface_name": "org.astarte-platform.standard-interfaces.GenericSensor",
    "version_major": 1,
    "version_minor": 0,
    "type": "datastream",
    "ownership": "device",
    "mappings": [
        {
            "endpoint": "/%{sensor_id}/value",
            "type": "double"
        }
    ]
}

    "interface_name": "org.astarte-platform.standard-interfaces.AvailableSensors",
    "version_major": 1,
    "version_minor": 0,
    "type": "property",
    "ownership": "device",
    "mappings": [
        {
            "endpoint": "/%{sensor_id}/name",
            "type": "string"
        },
        {
            "endpoint": "/%{sensor_id}/unit",
            "type": "string"
        }
    ]
}