fix: fail for non-array constraint in @IsIn decorator

[NoNameProvided]

Description

This PR fixes an error in @IsIn decorator that allowed values to pass validation when the constraint was not an array.

Checklist

• the pull request title describes what this PR does (not a vague title like Update index.md)
• the pull request targets the default branch of the repository (develop)
• the code follows the established code style of the repository
  • npm run prettier:check passes
  • npm run lint:check passes
• tests are added for the changes I made (if any source code was modified)
• documentation added or updated
• I have run the project locally and verified that there are no errors

Fixes

references #1693

[github-actions]

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