Improve encode_key docs
Improve encode_key docs

DualSpark/rust-aws,mthjones/rusoto,DualSpark/rusoto,DualSpark/rust-aws,mattico/rusoto,DualSpark/rusoto,mthjones/rusoto,DualSpark/rust-aws,mattico/rusoto,DualSpark/rusoto,SecurityInsanity/rusoto,mattico/rusoto,rusoto/rusoto,rusoto/rusoto,rusoto/rusoto,SecurityInsanity/rusoto