Automatically create a Kubernetes cluster during group creation
Description
Users that create a new group are encouraged to use Review Apps and to deploy their applications on a Kubernetes cluster. This requires adding a cluster to the group in a second moment. Adding the ability to create a new cluster (or to select an existing one) during the new group creation flow will make the experience easy.
Proposal
Add the ability to create a new Kubernetes cluster on GKE during the new group creation. As an additional step, we can list existing clusters in the specific GCP account (after the user signed in with OAuth2) and show a dropdown to choose existing clusters from the list, in case users want to use a cluster for multiple groups.
Note:
- This requires https://gitlab.com/gitlab-org/gitlab-ce/issues/34758 first
- This is the group version of https://gitlab.com/gitlab-org/gitlab-ce/issues/42042