Bug with delayed next routers server-centric routing

[LarsFlieger]

Describe the bug
The next router is server-centric which means the routing is done in the server and only if the request comes back the user gets redirected to the new url. When the user is doing actions while the server is loading which affects the routing, the new action will get overwritten with the old one which comes back. This causes issues with slow internet connections or test envs.

Related while dev:
#195

The upcoming router has fixed this problem. We have to wait till it's stable: https://beta.nextjs.org/docs/routing/loading-ui