fix: type correctness issues, error body preservation, and get_did_document implementation#29

Onyx2406 wants to merge 2 commits into

interledger:maininterledger/open-payments-rust:mainfrom

Onyx2406:fix/outgoing-payment-optional-spent-amountsOnyx2406/open-payments-rust:fix/outgoing-payment-optional-spent-amountsCopy head branch name to clipboard