Associate clusters model to groups34758-create-group-clusters

Even though we currently only should have one group for a cluster, we
allow the flexibility to associate to other groups in the future.

This also matches the runner <=> groups association.

- Adds Cluster#first_group, aliased to Cluster#group. For the
conceivable future, a cluster will have at most one group.

- Prevent mixing of group and project clusters. If project type
clusters, it should only have projects assigned.  Similarly with groups.

- Default cluster_type to :project_type. As it's very small table we can
set default and null: false in one release.

1 files changed, 2 insertions, 2 deletions

diff --git a/app/services/clusters/create_service.rb b/app/services/clusters/create_service.rb
index c6e955800af..cd843b8ffa8 100644
--- a/app/services/clusters/create_service.rb
+++ b/app/services/clusters/create_service.rb
@@ -9,9 +9,9 @@ module Clusters
     end
 
     def execute(project:, access_token: nil)
-      raise ArgumentError.new(_('Instance does not support multiple Kubernetes clusters')) unless can_create_cluster?(project)
+      raise ArgumentError, _('Instance does not support multiple Kubernetes clusters') unless can_create_cluster?(project)
 
-      cluster_params = params.merge(user: current_user, projects: [project])
+      cluster_params = params.merge(user: current_user, cluster_type: :project_type, projects: [project])
       cluster_params[:provider_gcp_attributes].try do |provider|
         provider[:access_token] = access_token
       end