Tidy up homepage and navigation

app/policies/dsn_policy.rb

@@ -0,0 +1,49 @@
+# frozen_string_literal: true
+
+class DsnPolicy < ApplicationPolicy
+  def index?
+    current_user.present? && current_user.admin?
+  end
+
+  def show?
+    current_user.present? && current_user.admin?
+  end
+
+  def create?
+    current_user.present? && current_user.admin?
+  end
+
+  def new?
+    create?
+  end
+
+  def update?
+    current_user.present? && current_user.admin?
+  end
+
+  def edit?
+    update?
+  end
+
+  def destroy?
+    current_user.present? && current_user.admin?
+  end
+
+  def disable?
+    current_user.present? && current_user.admin?
+  end
+
+  def enable?
+    current_user.present? && current_user.admin?
+  end
+
+  class Scope < Scope
+    def resolve
+      if user&.admin?
+        scope.all
+      else
+        scope.none
+      end
+    end
+  end
+end