use email address for unique-ish id for feature toggles (#3323)

* use email address for unique-ish id for feature toggles
* no need for user prefix any more

app/models/user.rb

@@ -290,7 +290,7 @@ def power_of_attorney
   end
 
   def flipper_id
-    "User;#{account_uuid}"
+    email || account_uuid
   end
 
   private

spec/models/user_spec.rb

@@ -383,6 +383,13 @@
     end
   end
 
+  describe '#flipper_id' do
+    let(:user) { build(:user, :loa3) }
+    it 'should return a unique identifier of email' do
+      expect(user.flipper_id).to eq(user.email)
+    end
+  end
+
   describe '#va_patient?' do
     let(:user) { build(:user, :loa3) }