ui-chart: allow changing series name when using JSON type

[mereshow]

Description

The documentation says:

Alternatively, you can set the series property to type JSON, and then provide an array of keys (e.g. ["key1", "key2"]), which will plot a data point for each key provided, from a single data point.

It would be nice to be able to change the names of the series, as the keys are usually "ugly". I think it could be solved allowing the property to be a JSON object, with the keys being the object keys, and each value the desired series name, such as:

{
    "value": "Series 1",
    "nested.value": "Series 2"
}

Have you provided an initial effort estimate for this issue?

I can not provide an initial effort estimate