Charts: Add "Show legend" option for "Default" charts

[hreichert]

The ESH DefaultChartProvider recently got a new feature to hide the legend:
eclipse-archived/smarthome#4291

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• Add the Option "Show legend" to the chart settings. Only shown if the "Default" chart is selected.
  • "automatic" -> let the chart provider decide (current behaviour: hide if there is only one chart series, show otherwise)
  • "always" -> force show
  • "never" -> force hide
• Send legend=true/false to the chart servlet, if "always" or "never" is choosen. If "automatic" is selected, do not send the paramater, as this triggers the automatic decision.

Chart settings:

Setting Show legend: Never results in:

[ghys]

Great!
Just one minor nitpick:

Around line 327 here:
https://github.com/openhab/org.openhab.ui.habpanel/pull/229/files#diff-ec117370212c2c630426d1b711598a6eR327

can you add something along the lines of

if (widget.charttype !== "default") {
    delete widget.showlegend;
}

to make sure the option doesn't appear in the models of the non-default charts.

Thanks ;)

[hreichert]

Sure, here you go!

[ghys]

Thanks again @hreichert!