Follow-up from "Implement enabled field in runner controller"

Summary

This issue tracks a follow-up from !215485 (merged) to standardize the error response format in the runner controllers API endpoints.

Problem

The runner controllers API endpoints currently return validation errors as a sentence string using errors.full_messages.to_sentence:

bad_request!(controller.errors.full_messages.to_sentence)

This is one of the only places in the entire codebase where to_sentence is used for error responses. The typical pattern in GitLab's REST API returns errors as an array of strings for consistency.

Proposal

Refactor the error responses in lib/api/ci/runner_controllers.rb to use the standard array format, aligning with the majority of the API codebase.

Timeline

This should be addressed before GA to avoid introducing a breaking change to the API response format.

The following discussion from !215485 (merged) should be addressed:

  • @habdul-razak started a discussion: (+2 comments)

    Questions (non-blocking):

    Why choose to return a sentence vs the usual array of strings? Is it a runner controller/cells specific thing?

Edited by 🤖 GitLab Bot 🤖