Starting this out pretty broad as it can cover a lot. Some ideas:
- Normal intro/readme type stuff
- User guide - how to run in standalone/distributed mode. Connector/tasks concepts and what they mean in practice. Fault tolerance & offsets. REST interface, Copycat as a service, etc.
- Dev guide - connectors/partitions/records/offsets/tasks. All the APIs, specific examples for implementing APIs, resuming from previous offsets, dynamic sets of partitions, how to work with the runtime data API, etc.
- System design - KIP-26 + more - why we ended up on the design we did, comparisons to other systems w/ low level details,