Towards a v1.0

Originally from #557

Possible Tasks

Items that should be discussed whether we should do right now.

Codebase
- TODOs
  - https://github.com/interledger-rs/interledger-rs/blob/master/crates/ilp-cli/src/interpreter.rs#L297
- Relax our traits #590
- change some pub items to pub(crate)
- HTTP APIs #128 #320
- gRPC version of APIs #418
- Decide whether to keep interledger_service::{IncomingService,OutgoingService} or switch to tower #434
- Ideally, decouple services from a specific future executor (would require a standardized task::spawn, as described in this blog post)
- Possibly rethink what to do with the grab bag that is interledger_service_util / where to put small services or how to combine them
- Improve error handlings #317 #354
- Horizontally scalable node #297 #40
- Exchange rate problem #256 #273
- Consider renaming settlement related variables #120
- Support OPay
- Crash recovery #176
- Stabilize Protocols
  - Stream #513 #467 #315 #154 #68 #50 #44
  - BTP #363
  - CCP #322
GUI
- Node management GUI
Documents
- per-argument docs
- Decide the methodology of providing docs (rust-doc, website, or both)
- Document balances and how to configure settlement parameters #593
Tests
- Performance tests #549 #87

The following should be items that we have agreed with (What we'll do).

API, configs, etc that the actual end-users would face to:

Stabilize HTTP API #364
Stabilize config options #425
Thorough testing to ensure no major bugs or performance issues
Stabilize log format and ensure we have enough #522
Stable support for 1+ databases / stores
More documentation (maybe #240 or #378)
- Document all the public items in the codebase
- Document for DockerHub #424
Ensure the interoperability with the other connectors (JS/Java).

Known-issues, structure that might need to be refactored, etc:

TBD, considering the dependency.

Make the list exhaustive
- Do stocktaking of TODOs in the codebase
- Check all the issues
Discuss what needs to be done
Decide the order
- Refactor the crate hierarchy
- Feature 0.3
- etc