CI Lint endpoint is broken (404)

Summary

The API method POST /api/v4/ci/lint returns a 404.

We are using this API endpoint to validate a library of GitLab CI/CD templates. This API method was working flawlessly until our upgrade from 15.7.7 to 16.2.3.

I can reproduce it on https://gitlab.com too.

Steps to reproduce

Two choices :

1. Follow the example https://docs.gitlab.com/ee/api/lint.html#use-jq-to-create-and-process-yaml--json-payloads
2. Use https://python-gitlab.readthedocs.io/en/stable/cli-examples.html#ci-lint

jq --null-input --arg yaml "$(<example-gitlab-ci.yml)" '.content=$yaml' | curl "https://gitlab.com/api/v4/ci/lint?include_merged_yaml=true" --header 'Content-Type: application/json' --data @-

Example Project

Already described in your documentation.

What is the current bug behavior?

{"error":"404 Not Found"}

What is the expected correct behavior?

Having the CI validated ...

Output of checks

Possible fixes

Drinking a coffee and reading code for spotting the bug.