Investigate need for linter on nullable fields in GraphQL
There was an incident due to a field that should have been nullable not being nullable. This API was created before we recommended making fields nullable.
We started discussing whether or not this should be audited and/or a linter added in https://gitlab.com/gitlab-com/feature-change-locks/-/issues/59#note_1842272802, but creating this issue so this investigation can be prioritized by the team currently responsible for our GraphQL API.
/cc @wortschi