Move permissions check to cluster subclass

app/services/metrics/dashboard/base_service.rb

@@ -38,13 +38,9 @@ module Metrics
       # Determines whether users should be able to view
       # dashboards at all.
       def allowed?
-        if params[:environment]
-          Ability.allowed?(current_user, :read_environment, project)
-        elsif params[:cluster]
-          true # Authorization handled at controller level
-        else
-          false
-        end
+        return false unless params[:environment]
+
+        Ability.allowed?(current_user, :read_environment, project)
       end
 
       # Returns a new dashboard Hash, supplemented with DB info

ee/app/services/metrics/dashboard/cluster_dashboard_service.rb

@@ -13,6 +13,11 @@ module Metrics
         STAGES::ClusterEndpointInserter,
         STAGES::Sorter
       ].freeze
+
+      # Permissions are handled at the controller level
+      def allowed?
+        true
+      end
     end
   end
 end