chore(deps): update oapi-codegen/actions action to v0.8.0 (#54)

Co-authored-by: renovate[bot] <29139614+renovate[bot]@users.noreply.github.com>

fix(deps): update module github.com/getkin/kin-openapi to v0.124.0

Merge pull request #7 from oapi-codegen/chore/testutil

Remove `testutil` dependency

Add gitignore