feat(billing): add invoices datasource

[yfodil]

No description provided.

[codecov-commenter]

Codecov Report

Attention: 3 lines in your changes are missing coverage. Please review.

Comparison is base (1b10703) 73.16% compared to head (3ec9884) 73.23%.

Additional details and impacted files

@@            Coverage Diff             @@
##           master    #2171      +/-   ##
==========================================
+ Coverage   73.16%   73.23%   +0.07%     
==========================================
  Files         209      211       +2     
  Lines       32991    33094     +103     
==========================================
+ Hits        24138    24238     +100     
- Misses       6762     6764       +2     
- Partials     2091     2092       +1     

Files	Coverage Δ
scaleway/helpers_billing.go	100.00% <100.00%> (ø)
scaleway/provider.go	80.88% <100.00%> (+0.05%)	⬆️
scaleway/data_source_billing_invoices.go	96.96% <96.96%> (ø)

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