$expand support in REST

I know it's been asked multiple times, but the issues are years old and I think there's no reason for DAB to not support relationships in REST given that OData does, efcore (which is a different thing but it's still a "db query to complex object" thing) and even competitors like supabase. It's an essential feature and many companies now gravitate around openapi specs (with generators like kiota) so graphql is just not an option