Maintain checkbox state in issue descriptions

When you toggle a checkbox in the issue description, your current local state always overrides the server state. This is problematic when someone else toggles a checkbox on the issue while you are viewing it. Any change you now make undos the change someone else made.

For those of us working at GitLab, this commonly occurs on Onboarding issues (as they have a large, collaborative todo list)

Actual behavior

If you toggle a checkbox without refreshing the page, you will inadvertently undo any changes someone else has made to the issue since you have had it open.

Expected behavior

Ideal

The ideal would be that the issue body is always real time and up to date. This would come with #4199 (moved). However, I understand that real time editing is a significant amount of work

Short term

It is really frustrating to unexpectedly lose state and have to correct the changes. In the short term, is there any thing we can do to address this issue. For example, can we add a callout on the page if the issue has been updated since you have loaded the page, and prompt you to refresh?