Add tests for the cors endpoint success and error paths

[mikewheeleer]

Cover the cors endpoint behaviour

Description

The cors endpoint family is under-tested around its error and edge paths. This issue adds focused integration tests.

Requirements and context

• Repository scope: StableRoute-Org/Stableroute-backend only.
• Add tests for success, not-found, validation-failure, and idempotent-repeat paths of cors.
• Assert status codes, error codes, and response shapes.
• Do not change behaviour unless a defect is found (note it).

Suggested execution

• Fork the repo and create a branch
• git checkout -b test/cors-01-endpoint
• Implement changes
  • Write code in: the relevant module.
  • Write comprehensive tests in: cover the new behaviour and edge cases.
• Test and commit

Test and commit

• Run npm run lint, npm test, and npm run build.
• Cover edge cases: not-found, invalid input, duplicate, empty result.
• Include the full test output in the PR description.

Example commit message

test(cors): cover success and error paths

Guidelines

• Minimum 95 percent test coverage for impacted modules.
• Clear, reviewer-focused documentation.
• Timeframe: 96 hours.

Community & contribution rewards

• 💬 Join the StableRoute community on Discord: https://discord.gg/37aCpusvx
• ⭐ This is a GrantFox OSS / Official Campaign task and may be rewarded. When your PR is merged you'll be prompted to rate the project — a 5-star rating is much appreciated.