fix: Add recentupdated as recognized sort option

- Add `recentupdated` to the `OrderByMap`.
- Add integration testing for organization and user repository sorting.
- Resolves #5612
- Regression from 12e23ee199 where the
`recentupdated` case was not added to the map, but was handled
seperately as a fallback. The regression came into affect when
5a0bc35799 also relied on this map but
didn't handle the `recentupdated` case.

models/repo/search.go

@@ -36,6 +36,7 @@ var OrderByMap = map[string]map[string]db.SearchOrderBy{
 var OrderByFlatMap = map[string]db.SearchOrderBy{
 	"newest":                OrderByMap["desc"]["created"],
 	"oldest":                OrderByMap["asc"]["created"],
+	"recentupdate":          OrderByMap["desc"]["updated"],
 	"leastupdate":           OrderByMap["asc"]["updated"],
 	"reversealphabetically": OrderByMap["desc"]["alpha"],
 	"alphabetically":        OrderByMap["asc"]["alpha"],