Option to offer end of war before a forced truce is possible

Originated from this thread:
https://www.games2gether.com/endless-space-2/forum/114-bug-reports/thread/22479-unable-to-end-war

Currently if you want to end war the system won't allow you too.

Either side needs to get enough of an advantage for the other for force a truce.

You cannot simply say:

"I reached my goals and don't need to exterminate that empire"

The game responds:
"You cannot stop. You need to keep on killing / pillaging / fighting"

Refusal of such a proposal should have no negative consequences.

But you could link it with a trade agreement if what you are fighting for is passage for your trade ships to another empire for example.