Update openai-php/client version to 0.18 (#38)

Merge pull request #37 from GromNaN/phpunit

- Remove required config `openai.api_key`
- Use PhpUnit directly

Refactor as a single-class bundle (#33)

deps: update openai-php/client v0.16 (#32)

Bump openai-php/client to 0.15 (#30)

deps: allow openai-php/client v0.13 (#27)

Update CHANGELOG for v0.12.0

chore: don't tests against lower

Prepare v0.10.0 (#20)

Merge pull request #16 from frithjof/main

add assistant beta header to make it possible to use assistants