Fix N+1 querying GraphQL for subgroupMilestone
What does this MR do and why?
Related to #218975 (closed)
Using TDD I wrote a failing spec to prove N+1 violation.
I then added the preload/lookahead and the spec is now passing.
MR acceptance checklist
This checklist encourages us to confirm any changes have been analyzed to reduce risks in quality, performance, reliability, security, and maintainability.
-
I have evaluated the MR acceptance checklist for this MR.