[Validator] Add check for existing metadata on property

| Q             | A
| ------------- | ---
| Bug fix?      | no (sort of)
| New feature?  | no
| BC breaks?    | no (I don't think so)
| Deprecations? | no
| Tests pass?   | yes
| Fixed tickets | ~
| License       | MIT
| Doc PR        | ~

Todo:
- [x] Check if the new method should be added to the interface as well.

This adds a check for metadata existence before usage else the code will emit a warning.

This should not be a BC break or a bug fix as the patched code is 2.2 specific.

@bschussek let me know if I should add the method in the interface as well. Thank you.