feat(plugin-chart-echarts): add support for custom forecasts

[villebro]

🏆 Enhancements

The need to be able to create custom forecasts (without Prophet) has come up. In order to make this possible, we will assume that a forecast is present if there is a series with the forecast suffix (__yhat, __yhat_lower or __yhat_upper).

This is an intermediate step to decouple forecasts from Prophet - ultimately we should refactor the code in the following ways:

• move the relevant utilities/types from plugin-chart-echarts to superset-ui/core
• add support for other suffixes to make it possible to do similar inference from time offset series etc. Example: my_metric could be accompanied by my_metric__offset(PT1D) which could then be shown in the legend (with translations) as "my metric (1 day time offset)" or similar.
• Add documentation for how these can be used.

SCREENSHOTS

Notice, that I haven't enabled forecasting, yet I'm able to create a chart with a forecast and confidence interval by applying the necessary suffixes to the series names:

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[codecov]

Codecov Report

Merging #1389 (f26c6f5) into master (63c9ca6) will increase coverage by 0.06%.
The diff coverage is 73.33%.

@@            Coverage Diff             @@
##           master    #1389      +/-   ##
==========================================
+ Coverage   30.34%   30.41%   +0.06%     
==========================================
  Files         497      497              
  Lines        9979     9990      +11     
  Branches     1680     1684       +4     
==========================================
+ Hits         3028     3038      +10     
- Misses       6706     6707       +1     
  Partials      245      245              

Impacted Files	Coverage Δ
...lugin-chart-echarts/src/Timeseries/transformers.ts	44.14% <20.00%> (-0.31%)	⬇️
...gin-chart-echarts/src/Timeseries/transformProps.ts	55.12% <100.00%> (+1.18%)	⬆️
plugins/plugin-chart-echarts/src/utils/prophet.ts	92.98% <100.00%> (+2.78%)	⬆️
...ackages/superset-ui-core/src/utils/featureFlags.ts	100.00% <0.00%> (ø)
...ns/legacy-plugin-chart-histogram/src/Histogram.jsx	0.00% <0.00%> (ø)
...egacy-plugin-chart-histogram/src/transformProps.js	0.00% <0.00%> (ø)

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[BillGreerUX]

Thank you, this fits our use-case we requested to allow us to create custom forecasts without Prophet.

[zhaoyongjie]

I got a weird area when create a custom forecasts

[villebro]

I got a weird area when create a custom forecasts

Oh, I think it's because your lower bound (SUM(num) * 1.2) is above the upper bound (SUM(num) * 1.1).

[zhaoyongjie]

tested in local. LGTM

[zhaoyongjie]

I got a weird area when create a custom forecasts

Oh, I think it's because your lower bound (SUM(num) * 1.2) is above the upper bound (SUM(num) * 1.1).

Thanks! You are right.