Notifications settings should cascade from project, through each group, and then to the global setting if “Global” is set on the project or any of the groups * if user has project notification settings - use those. * If it defaults to `Global` then look for parent notification settings. * If parent defaults to `Global` too, then look one level up and up until we find something. So basically same behavior like we had before with project/group but with possible N subgroups in between. See https://gitlab.com/gitlab-org/gitlab-ce/issues/30549#note_28268440 comment for further details.