Changing mapping rules of one backend API affects position of mapping rules of other backend APIs.

If backend A has 2 mapping rules ordered 1 and 2 and the user creates under a second backend B a third mapping rule, the third mapping rule will have position 1 and backend A's mapping rules will be updated to positions 2 and 3.

We must ensure that changing mapping rules under one backend API only affects positions of other mapping rules under the same backend API, not leaking to others.