Split schema for roles API

[api-clients-generation-pipeline]

See DataDog/datadog-api-spec#428

[therve]

/azp run

[azure-pipelines]

Azure Pipelines successfully started running 1 pipeline(s).

[codecov]

Codecov Report

Merging #337 into master will decrease coverage by 0.06%.
The diff coverage is 6.82%.

Impacted Files	Coverage Δ
api/v2/datadog/model_role_attributes.go	11.70% <0.00%> (-2.59%)	⬇️
api/v2/datadog/model_role_create_attributes.go	15.58% <0.00%> (-12.33%)	⬇️
api/v2/datadog/model_role_update_attributes.go	19.48% <0.00%> (-15.41%)	⬇️
api/v2/datadog/model_role_update_response_data.go	2.15% <2.15%> (ø)
api/v2/datadog/model_role_create_response_data.go	4.30% <4.30%> (ø)
api/v2/datadog/model_role_create_response.go	4.65% <4.65%> (ø)
api/v2/datadog/model_role_update_response.go	4.65% <4.65%> (ø)
...pi/v2/datadog/model_role_response_relationships.go	11.62% <15.38%> (+8.43%)	⬆️
api/v2/datadog/model_role_create_request.go	23.25% <23.52%> (ø)
api/v2/datadog/model_role_update_request.go	30.23% <35.29%> (ø)
... and 11 more