feat: display valid enum values for "isEnum" errors

[hood]

Description

This PR changes the error message for @IsEnum() decorator to include possible options.

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 #837

[hood]

Is this ever gonna be merged?

[hood]

Is this ever going to be merged?

[ozburo]

Yes, please merge so we don't have to create custom error messages just to show possible enum values xD

[hesalx]

Implicitly defined enums actually start with 0 and due to type coercion this check is not reliable.

If you define

  enum MyEnum {
    First,
    Second,
  }

one of the entries is ['0', 'First'], and !parseInt('0') === !0 === true
and the return value for MyEnum will be ['First', '0', 1'] instead of the expected ['0', '1'].

It would be more reliable to check whether the key is not a number after all, like:

Suggested change

	.filter(entry => !parseInt(entry[0]))
	.filter(entry => isNaN(parseInt(entry[0])))

[NoNameProvided]

Superset by #1826.

[github-actions]

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