message: Add Error variant for String::from_utf8 error
diff: @@ -46,6 +46,12 @@ pub enum Error {
  #[cfg(feature = "backtraces")]
  backtrace: snafu::Backtrace,
  },
  + #[snafu(display("UTF8 encoding error: {}", source))]
  + Utf8StringErr {
  + source: std::string::FromUtf8Error,
  + #[cfg(feature = "backtraces")]
  + backtrace: snafu::Backtrace,
  + },
  #[snafu(display("Unauthorized"))]
  Unauthorized {
  #[cfg(feature = "backtraces")]
  