When removing an issue from a board should also remove associated milestone from issue

Scenario 1

• Currently when removing an issue from a board, all the list labels on the board are removed from the issue
• If the board has an associated milestone, that associated milestone should also be removed from the issue

Scenario 2

• Same thing as above, but for a board without an associated milestone, but a dropdown filtered milestone
• When a dropdown milestone is selected, removing an issue from the board should remove the issue's milestone too

added ~12980 label

added ~579196 label

cc @jschatz1 @iamphill @cperessini

added ~874211 label

@victorwu i agree with this first scenario. But not the second, I dont think we should take into consideration the filters when doing anything with issues.

assigned to @iamphill

Thanks @iamphill! Let's lean on your preference for now. I crossed out the temp filtering scenario for this one and https://gitlab.com/gitlab-org/gitlab-ce/issues/29612

I don't think we should take filters into account either because they are just temporarily items and not part of the definition of the board

closed via merge request gitlab-ee!1446

mentioned in merge request !14785