Prevent cluster migration spec from interfering with later specs

If a later spec tries to set a field that is added to any of these models by a
later migration than the GCP clusters migration, it will fail because the
model's columns are cached.

We should always refer to models in migration specs by either their class in the
migration, or the table directly, using the `table` helper.

spec/migrations/migrate_gcp_clusters_to_new_clusters_architectures_spec.rb

@@ -33,7 +33,7 @@ describe MigrateGcpClustersToNewClustersArchitectures, :migration do
     let(:encrypted_gcp_token) { "'encrypted_gcp_token'" }
     let(:encrypted_gcp_token_iv) { "'encrypted_gcp_token_iv'" }
 
-    let(:cluster) { Clusters::Cluster.last }
+    let(:cluster) { described_class::Cluster.last }
     let(:cluster_id) { cluster.id }
 
     before do
@@ -46,12 +46,12 @@ describe MigrateGcpClustersToNewClustersArchitectures, :migration do
     it 'correctly migrate to new clusters architectures' do
       migrate!
 
-      expect(Clusters::Cluster.count).to eq(1)
-      expect(Clusters::Project.count).to eq(1)
-      expect(Clusters::Providers::Gcp.count).to eq(1)
-      expect(Clusters::Platforms::Kubernetes.count).to eq(1)
+      expect(described_class::Cluster.count).to eq(1)
+      expect(described_class::ClustersProject.count).to eq(1)
+      expect(described_class::ProvidersGcp.count).to eq(1)
+      expect(described_class::PlatformsKubernetes.count).to eq(1)
 
-      expect(cluster.user).to eq(user)
+      expect(cluster.user_id).to eq(user.id)
       expect(cluster.enabled).to be_truthy
       expect(cluster.name).to eq(gcp_cluster_name.delete!("'"))
       expect(cluster.provider_type).to eq('gcp')
@@ -59,7 +59,7 @@ describe MigrateGcpClustersToNewClustersArchitectures, :migration do
 
       expect(cluster.project_ids).to include(project.id)
 
-      expect(cluster.provider_gcp.cluster).to eq(cluster)
+      expect(cluster.provider_gcp.cluster_id).to eq(cluster.id)
       expect(cluster.provider_gcp.status).to eq(status)
       expect(cluster.provider_gcp.status_reason).to eq(tr(status_reason))
       expect(cluster.provider_gcp.gcp_project_id).to eq(tr(gcp_project_id))
@@ -71,7 +71,7 @@ describe MigrateGcpClustersToNewClustersArchitectures, :migration do
       expect(cluster.provider_gcp.encrypted_access_token).to eq(tr(encrypted_gcp_token))
       expect(cluster.provider_gcp.encrypted_access_token_iv).to eq(tr(encrypted_gcp_token_iv))
 
-      expect(cluster.platform_kubernetes.cluster).to eq(cluster)
+      expect(cluster.platform_kubernetes.cluster_id).to eq(cluster.id)
       expect(cluster.platform_kubernetes.api_url).to be_nil
       expect(cluster.platform_kubernetes.ca_cert).to be_nil
       expect(cluster.platform_kubernetes.namespace).to eq(tr(project_namespace))
@@ -109,7 +109,7 @@ describe MigrateGcpClustersToNewClustersArchitectures, :migration do
     let(:encrypted_gcp_token) { "'encrypted_gcp_token'" }
     let(:encrypted_gcp_token_iv) { "'encrypted_gcp_token_iv'" }
 
-    let(:cluster) { Clusters::Cluster.last }
+    let(:cluster) { described_class::Cluster.last }
     let(:cluster_id) { cluster.id }
 
     before do
@@ -122,12 +122,12 @@ describe MigrateGcpClustersToNewClustersArchitectures, :migration do
     it 'correctly migrate to new clusters architectures' do
       migrate!
 
-      expect(Clusters::Cluster.count).to eq(1)
-      expect(Clusters::Project.count).to eq(1)
-      expect(Clusters::Providers::Gcp.count).to eq(1)
-      expect(Clusters::Platforms::Kubernetes.count).to eq(1)
+      expect(described_class::Cluster.count).to eq(1)
+      expect(described_class::ClustersProject.count).to eq(1)
+      expect(described_class::ProvidersGcp.count).to eq(1)
+      expect(described_class::PlatformsKubernetes.count).to eq(1)
 
-      expect(cluster.user).to eq(user)
+      expect(cluster.user_id).to eq(user.id)
       expect(cluster.enabled).to be_truthy
       expect(cluster.name).to eq(tr(gcp_cluster_name))
       expect(cluster.provider_type).to eq('gcp')
@@ -135,7 +135,7 @@ describe MigrateGcpClustersToNewClustersArchitectures, :migration do
 
       expect(cluster.project_ids).to include(project.id)
 
-      expect(cluster.provider_gcp.cluster).to eq(cluster)
+      expect(cluster.provider_gcp.cluster_id).to eq(cluster.id)
       expect(cluster.provider_gcp.status).to eq(status)
       expect(cluster.provider_gcp.status_reason).to eq(tr(status_reason))
       expect(cluster.provider_gcp.gcp_project_id).to eq(tr(gcp_project_id))
@@ -147,7 +147,7 @@ describe MigrateGcpClustersToNewClustersArchitectures, :migration do
       expect(cluster.provider_gcp.encrypted_access_token).to eq(tr(encrypted_gcp_token))
       expect(cluster.provider_gcp.encrypted_access_token_iv).to eq(tr(encrypted_gcp_token_iv))
 
-      expect(cluster.platform_kubernetes.cluster).to eq(cluster)
+      expect(cluster.platform_kubernetes.cluster_id).to eq(cluster.id)
       expect(cluster.platform_kubernetes.api_url).to eq('https://' + tr(endpoint))
       expect(cluster.platform_kubernetes.ca_cert).to eq(tr(ca_cert))
       expect(cluster.platform_kubernetes.namespace).to eq(tr(project_namespace))