https://cloud.google.com/iam/docs/reference/credentials/rest/v1/projects.serviceAccounts/signBlob
Options passed to Req.new/1 can be extended via the :req_options application
environment, e.g. config :gcs_signed_url, :req_options, plug: {Req.Test, GcsSignedUrl.SignBlob.HTTP}.
Summary
Functions
@spec post(String.t(), map(), String.t()) :: {:ok, Req.Response.t()} | {:error, Exception.t()}