fix(emissions): update eMapsZonesResponse to match current Electricity Maps API

[samoz83]

Fixes #467

Problem

The Electricity Maps /v3/zones endpoint has changed its response schema. Zone objects now contain non-string typed fields:

Field	Old type	New type
subZoneKeys	did not exist / string	[]string (array)
isCommerciallyAvailable	did not exist	bool
zoneParentKey	string	string | null
tier	did not exist	string | null

The current type eMapsZonesResponse is defined as map[string]map[string]string, so json.Unmarshal fails when it encounters these non-string values: json: cannot unmarshal array into Go value of type string

This prevents ceems_exporter from starting when the [maps emissions provider is enabled.

Changes

• pkg/emissions/types.go: Replaced eMapsZonesResponse from map[string]map[string]string to map[string]eMapsZoneDetails, adding a new eMapsZoneDetails struct that properly models the current API response.
• pkg/emissions/emaps.go: Updated zone iteration to access struct fields (details.CountryName, details.ZoneName) instead of map indexing.
• pkg/emissions/emaps_test.go: Updated TestNewEMapsProvider to use the new eMapsZoneDetailsstruct.

Testing

All existing emissions tests pass and ceems_exporter runs:

=== RUN TestEMapsDataProvider 
--- PASS 
=== RUN TestEMapsDataProviderError 
--- PASS 
=== RUN TestNewEMapsProvider 
--- PASS
=== RUN TestNewEMapsProviderFail 
--- PASS 
=== RUN TestEMapsAPIRequest 
--- PASS 
=== RUN TestEMapsAPIRequestFail 
--- PASS 
=== RUN TestEMapsAPIRequestZones 
--- PASS

[mahendrapaipuri]

Thanks a lot @samoz83 for the PR. Really appreciate it!! Could you confirm me that this patch works as expected for you? If so, I will cut a release with this PR.

Cheers!!

[samoz83]

Yep, I can confirm that my node is now running the exporter and not failing to start due to the unmarshal array issue and pulling in emaps data:
ceems_emissions_gCo2_kWh{country="Great Britain",country_code="GB",provider="emaps",provider_name="Electricity Maps"} 165

[mahendrapaipuri]

Awesome @samoz83

Cheers again for the PR. Let me merge it and make a new release!

[mahendrapaipuri]

Between, are you using CEEMS in production @samoz83 ? If so, could I add that to the list of adopters?

Cheers!!

[samoz83]

@mahendrapaipuri Sure, we are using it in production on our AI@Surrey cluster at the University of Surrey