- Change all relative path imports to have `.js` suffix required by the
    ESM standard.
- Use full import path instead of directory default import.
- I've created a tool for doing this automatically (existing tools were
    failing on some edge cases). The sources
    are available here: https://github.com/outSH/to-esm-imports.
- The tool is executed after codegen (because openapi generators
    doesn't support creating ESM-compatible imports yet).
- Changed jest and webpack configs to work with
    fully qualified ESM imports.

Signed-off-by: Michal Bajer <michal.bajer@fujitsu.com>

feat(wip): additional import fixes

[skip ci]