Merge branch 'minac_408917_fix_disparity_between_rest_and_gql_apis' into 'master'

Use `Issue#readable_by` to solve disparity in APIs for issue links

See merge request https://gitlab.com/gitlab-org/gitlab/-/merge_requests/124201



Merged-by: Brian Williams <bwilliams@gitlab.com>
Approved-by: Brian Williams <bwilliams@gitlab.com>
Reviewed-by: Brian Williams <bwilliams@gitlab.com>
Co-authored-by: Mehmet Emin INAC <minac@gitlab.com>