Creating a new policy with the same ID as an existing policy "merges" them

[arielshaqed]

Reported by a user.

I tried to create a read policy but somehow instead of a new policy, the change is merged to an existing policy. [...] Thanks, I figured it out. I used GUI. I gave a new policy name, but in the JSON I copied, I forget to change the policy id, then lakeFS “smartly” merge it to existing policy instead of creating a new one.

(Emphasis mine)