Locking of an entity when it is actively being edited; phone beta

In WordPress, both on the /wp-admin area and in apps, an entity can be marked as locked with metadata about who is editing it and when they started, meaning that a user cannot inadvertently overwrite changes made by another if they're both editing. Ideally, the Invoice Ninja app would sync every x amount of time just to tell the Invoice Ninja instance "yes, this user is still editing this entity", so that anyone trying to edit it can see that it's currently being edited. With that said, WordPress also allows Take over alongside Exit editor as an option, so if someone has clocked off or run out of battery but left the thing running, you can optionally choose to start editing. Any changes the other user was making get saved to a "revision", and you start editing from there. This sort of thing is very important for anyone using the app in the field where you may have a phone call happening on parallel that may be about the same thing, but one user can tre…