Adding enable_mediated_deposit as a flippable feature

config/features.rb

@@ -7,4 +7,8 @@
   feature :assign_admin_set,
           default: true,
           description: "Ability to assign uploaded items to an admin set"
+
+  feature :enable_mediated_deposit,
+          default: false,
+          description: "Turn on mediation for all deposits"
 end

spec/models/flipflop_spec.rb

@@ -5,4 +5,8 @@
     subject { described_class.assign_admin_set? }
     it { is_expected.to be true }
   end
+  describe "enable_mediated_deposit?" do
+    subject { described_class.enable_mediated_deposit? }
+    it { is_expected.to be false }
+  end
 end