Would you accept a PR adding serde support behind a feature to block-modes? This could be used to implement multi part encryption APIs on top of block-modes. For example: you encrypt a couple of block, save the state, later, restore the state and encrypt a couple more blocks, save/restore, (etc.) finalize. This is a pretty standard paradigm in some legacy crypto APIs that I'd like to implement with a Rust backend.

cc @zugzwang