It was introduced in https://github.com/json-api-dotnet/JsonApiDotNetCore/pull/325, but then removed in https://github.com/json-api-dotnet/JsonApiDotNetCore/pull/619 for reasons unknown to me. https://github.com/dotnet/sourcelink/blob/master/docs/README.md