PDS proof of concept:
- ipld sqlite driver importing CAR file
- MST code to read and mutate state
- sqlite schema
- JSON schema type generation (separate crate?)
- write wrapper which updates MST *and* updates other tables in a transaction
- did:web thingie?
- HTTP API handler implementing most endpoints

libraries:
- `jsonschema` to validate requests and records (rich validation)
- `schemafy` to codegen serde types for records (ahead of time?)
- `rusqlite` with "bundled" sqlite for datastore
- `ipfs-sqlite-block-store` and `libipld` to parse and persist repo content 
- `warp` as async HTTP service
- `r2d2` to wrap rusqlite (?)
- pretty_env_logger
- ??? for CBOR (de)serialization of MST, separate from the IPLD stuff?
- no good crate for working with CAR files... could rip out this code?
    https://github.com/n0-computer/iroh/tree/main/iroh-car