Add positive validation testdata with valid RouteGroups

[vlktna]

Currently, our validation testdata primarily focuses on failure scenarios caused by technical debt in an early PR of the validation webhook. While these tests demonstrate how validation fails, they don’t ensure that valid RouteGroups pass correctly.

This gap means we might miss regressions where even valid RouteGroups start failing silently. To improve test coverage and reliability, we should:

• add a working set of valid RouteGroups that pass validation (OK cases)
• ensure webhook behavior is tested for both positive and negative outcomes

references
#3582
#3650