Pseudo-Integration tests for KMS (#239)

* wip

* Generate Cargo.toml after lib rs, cleanup deps

* Move RecordingConnection into an extras crate

* Move generation code into extras crate

* Delete unused conn method

* Add todo about storing req/resps externally

* Add note about credential expiry

* Fix clippy lint

* Replace creds with fake creds

* Delete note about real credentials

* Give cargo fmt a hand