Specifies the minimal API required from storage adapters.
@callback expand_path(filepath :: String.t()) :: String.t()
@callback expand_path(filepath :: String.t(), rootdir :: String.t()) :: String.t()
@callback read(filepath :: String.t()) :: {:ok, String.t()} | {:error, term()}
@callback read(filepath :: String.t(), rootdir :: String.t()) :: {:ok, String.t()} | {:error, term()}