Migrate SQL preview to new BYOC architecture #26
Description
The introduction of BYOC to Decodable brought along a change in architecture - a much clearer split between the control plane and data plane.
Previously, previews were started and fetched directly from the control plane API. After this change, authorization tokens have to be obtained from the control plane, while the preview is started and fetched from the data plane API.
See https://docs.decodable.co/reference/createpreviewtokens, https://docs.decodable.co/reference/createsqlpreview, https://docs.decodable.co/reference/getsqlpreview.