RoutePath save bug when having old routePath opened in tab and using that when saving

[Divinare]

Backend PR: https://gitlab.hsl.fi/jore/jore-map-backend/-/merge_requests/346

Steps:

1. Open the same routePath twice in 2 browser tabs
2. Save routePath in one tab
3. Save routePath again (without pressing f5) in other tab
4. Now routePath geometries are broken
   --> Reason: it saves both and geometry validation doesn't compare situation after save 1 to changes of save 2

How to fix?
Before saving, in addition to checking if routePaths are sync, check that the routePath sent is in sync with the routePath found in local DB. For example you can compare the edit timestamp of local db routePath & routePath being saved.