Add ability to differentiate between comment and TODO in MRs and block MR when there are open TODOs

Problem to solve

As a reviewer of an MR, I would like to be able to clearly communicate which topics need to be addressed before the MR can be merged. I would like to be able to configure the repository in such a way that the MR cannot be merged as long as there are such open topics. On the other hand, I also want to be able to simply add comments that are purely informative. These should not block the MR.

Current situation

My understanding is that GitLab only offers the ability to block the merge until all "threads" are resolved. But this means that even purely informative threads (such as a simple "Thumbs up!" for a particularly nice piece of code) have to be resolved to merge the MR. I have also seen that it is possible to define task boxes using the - [] syntax, but these do not seem to be treated different than a plain comment when it comes to blocking the merge.

Proposal

One way to fulfill the above request would be to add the option "All tasks must be resolved" to the merge checks. If you do this, then it should also be possible to create tasks from the GUI and not just via some special syntax.