Add feature tests for GitLab Duo pro bulk actions
What does this MR do and why?
This MR is covering the feature specs for the GitLab Duo Pro bulk actions:
Context
As part of https://gitlab.com/groups/gitlab-org/-/epics/11463+, we need to add happy scenarios feature specs coverage for bulk assign/unassign.
Original discussion: https://gitlab.com/groups/gitlab-org/-/epics/11463#note_1835025095
Scenarios we cover
- Successful bulk assignment
- Successful bulk un-assignment
- Not enough seats to assign to all selected members
Thoughts for reviewers' discussions: Please refer to the thought I am sharing here, I would like to hear the reviewers' opinions on that. I don't strongly advocate writing feature tests for scenarios involving a third-party actor like Cdot. In my perspective, feature tests should encompass a full system test without third-party mocks. Even if we were to write such specs, our inability to conduct a complete test cycle against the actual backend in Cdot remains a limitation. Consequently, we still fall short of performing a full system test.
Related to #454231