Fix span detail format

[scadu]

Format spans in format expected by Test Engine.

Since details type is changed from string to dict, this could be a breaking change, even though span details previously wouldn't work due to the type mismatch between collector and Test Engine.

[nprizal]

Hi @scadu, thanks for opening the PR. It looks great! I appreciate you adding the codedoc around the expected data structure for span details.

We’re planning to implement validation to prevent the collector from sending invalid span data but we’ll open a separate PR for that.

[nprizal]

Thanks for adding the validation 💚 . I think we want the detail to be required for sql, http, and annotation. Is that right @gchan @malclocke?

[gchan]

I think we want the detail to be required for sql, http, and annotation

Yep that's correct. Here's the reference which should be up-to-date and correct.
https://buildkite.com/docs/test-engine/test-collection/importing-json#json-test-results-data-reference-span-objects

[nprizal]

🚀

[scadu]

Thanks for the review @nprizal! I think it should be good to merge now?