[Feature Contribution]: Multiple data source support

What happened?

I proposed this feature in https://github.com/Green-Software-Foundation/carbon-aware-sdk/issues/343#issuecomment-1531014957 .

Carbon Aware SDK supports just one data source as following:

{
  "DataSources": {
    "EmissionsDataSource": "ElectricityMaps",
    "ForecastDataSource": "WattTime",

Granularity and covered area vary in each data souces. Some SDK users want to use WattTime as a first priority, but they might want to use ElectricityMaps when they want to know emission data of uncovered area in WattTime.

So I’d like to propose mutiple data source support as following:

{
  "DataSources": {
    "EmissionsDataSources": ["WattTime", "ElectricityMaps"],
    "ForecastDataSources": ["JSON", "WattTime", "ElectricityMaps"],

In above case, both EmissionsDataSouce and ForecastDataSouces are array. Lower index is higher priority. For example in EmissionData, WattTime is the highest priority, but no emission data for given location in WattTime, it would fallback to ElectricityMaps.

Code of Conduct

• I agree to follow this project’s Code of Conduct

Feature Commitment

• I commit to contributing this feature as a PR and working with the GSF to merge this feature into the Carbon Aware SDK.

[bderusha]

@YaSuenag This seems worthy of an ADR.

[Willmish]

Update from meeting #355: not crticial for 1.1, rather a feature for 1.2. Open to discussion