Create a signed upload URL that can be used to upload files to a bucket.
buckets table permissions: noneobjects table permissions: insertlet signedUploadUrl = try await supabase.storage
  .from("avatars")
  .createSignedUploadURL(path: "folder/avatar1.png")
let signedUploadUrl = try await supabase.storage
  .from("avatars")
  .createSignedUploadURL(
    path: "folder/avatar1.png",
    options: CreateSignedUploadURLOptions(
      upsert: true
    )
  )