chore: move List util out of db2sdk to avoid circular imports (#21733)

coderd/util/slice/slice.go

@@ -4,6 +4,25 @@ import (
 	"golang.org/x/exp/constraints"
 )
 
+// List is a helper function to reduce boilerplate when converting slices of
+// database types to slices of codersdk types.
+// Only works if the function takes a single argument.
+func List[F any, T any](list []F, convert func(F) T) []T {
+	return ListLazy(convert)(list)
+}
+
+// ListLazy returns the converter function for a list, but does not eval
+// the input. Helpful for combining the Map and the List functions.
+func ListLazy[F any, T any](convert func(F) T) func(list []F) []T {
+	return func(list []F) []T {
+		into := make([]T, 0, len(list))
+		for _, item := range list {
+			into = append(into, convert(item))
+		}
+		return into
+	}
+}
+
 // ToStrings works for any type where the base type is a string.
 func ToStrings[T ~string](a []T) []string {
 	tmp := make([]string, 0, len(a))