Changes per sneak's review:
- Delete docker-compose.yml, add example stanza to README
- Define custom domain types: ImageID, ContainerID, UnparsedURL
- Use custom types in all function signatures throughout codebase
- Restore imageID parameter (as domain.ImageID) in deploy pipeline
- buildContainerOptions now takes ImageID directly instead of
constructing image tag from deploymentID
- Fix pre-existing JS formatting (prettier)
make check passes with zero failures.
