feat(legacy-plugin-chart-country-map): added support for Legend options

[RoBYCoNTe]

SUMMARY

Country map seems to be not very clear when you have to see and check why specific color has been chosen for an area of the map. I think legend option is mandatory to improve readability of charts.

BEFORE/AFTER SCREENSHOTS OR ANIMATED GIF

Before was not possible to configure legend, now you can use specific parameters to obtain it:

I've added few new config props:

• LEGEND: allow to set position of the legend (None, Top, TopLeft, TopRight, Bottom, BottomLeft, BottomRight)
• ORIENTATION: vertical or horizontal (like a color gradient)
• FONT SIZE: used to render each step of the legend.

TESTING INSTRUCTIONS

Run the application and create a new chart of type Country Map, you will see new parameters that can be used to customize visualization of the chart.

ADDITIONAL INFORMATION

• Has associated issue:
• Required feature flags:
• Changes UI
• Includes DB Migration (follow approval process in SIP-59)
  • Migration is atomic, supports rollback & is backwards-compatible
  • Confirm DB migration upgrade and downgrade tested
  • Runtime estimates and downtime expectations provided
• Introduces new feature or API
• Removes existing feature or API

[codecov]

Codecov Report

Merging #22356 (74e74be) into master (ff1d29c) will decrease coverage by 0.06%.
The diff coverage is 3.79%.

❗ Current head 74e74be differs from pull request most recent head aba2fc0. Consider uploading reports for the commit aba2fc0 to get more accurate results

@@            Coverage Diff             @@
##           master   #22356      +/-   ##
==========================================
- Coverage   66.85%   66.78%   -0.07%     
==========================================
  Files        1847     1848       +1     
  Lines       70560    70638      +78     
  Branches     7737     7768      +31     
==========================================
+ Hits        47173    47176       +3     
- Misses      21380    21455      +75     
  Partials     2007     2007              

Flag	Coverage Δ
javascript	53.69% <3.79%> (-0.11%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
.../legacy-plugin-chart-country-map/src/CountryMap.js	0.00% <0.00%> (ø)
...s/legacy-plugin-chart-country-map/src/countries.ts	100.00% <ø> (ø)
...ins/legacy-plugin-chart-country-map/src/legend.tsx	0.00% <0.00%> (ø)
...acy-plugin-chart-country-map/src/transformProps.js	0.00% <ø> (ø)
...egacy-plugin-chart-country-map/src/controlPanel.ts	57.14% <60.00%> (+7.14%)	⬆️

📣 We’re building smart automated test selection to slash your CI/CD build times. Learn more

[igamat]

Hi @RoBYCoNTe,
I am currently working with Superset and I definitely see this feat as a must to be included in the Country map options. However, I see there's a small issue with the legend values as in the BEFORE/AFTER SCREENSHOT image the last two value ranges are overlapping. Is that the expected behavior or is that a mistake ? In that case, how can this issue be solved ?
Thank you.