[Engineering] Continuous onboarding
## Overview This epic holds the two engineering issues for the continuous onboarding work described in the [parent epic](https://gitlab.com/groups/gitlab-org/-/epics/4817). The ~"group::conversion" team will work on building design 1A https://gitlab.com/gitlab-org/gitlab/-/issues/281022 The ~"group::activation" team will work on building design 1B https://gitlab.com/gitlab-org/growth/team-tasks/-/issues/306 ## Experiment roll out and tracking: In order to successfully track this experiment, we will utilize a shared feature flag to allow for 33% of traffic to get the control, 33% of the traffic to get design 1A and 33% of the traffic to get design 1B. We will utilize a shared experiment tracking issue which is linked in the parent epic but also linked here https://gitlab.com/gitlab-org/gitlab/-/issues/281024
epic