add "archived" workflow state to rubric models

closes EVAL-3659
flag=enhanced_rubrics

test plan:
- tests pass

Change-Id: I264dd9141bda8cb9039249ab07a2ddcecd5ac653
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/332498
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Christopher Soto <christopher.soto@instructure.com>
Reviewed-by: Kai Bjorkman <kbjorkman@instructure.com>
QA-Review: Derek Williams <derek.williams@instructure.com>
Product-Review: Cameron Ray <cameron.ray@instructure.com>

app/models/rubric.rb

@@ -95,10 +95,25 @@ class Rubric < ActiveRecord::Base
   end
 
   workflow do
-    state :active
+    state :active do
+      event :archive, transitions_to: :archived
+    end
+    state :archived do
+      event :unarchive, transitions_to: :active
+    end
     state :deleted
   end
 
+  def archive
+    # overrides 'archive' event in workflow to make sure the feature flag is enabled
+    # remove this and 'unarchive' method when feature flag is removed
+    super if enhanced_rubrics_enabled?
+  end
+
+  def unarchive
+    super if enhanced_rubrics_enabled?
+  end
+
   def self.aligned_to_outcomes
     where(
       ContentTag.learning_outcome_alignments
@@ -468,4 +483,8 @@ class Rubric < ActiveRecord::Base
         context&.root_account_id
       end
   end
+
+  def enhanced_rubrics_enabled?
+    Account.site_admin.feature_enabled?(:enhanced_rubrics)
+  end
 end

spec/models/rubric_spec.rb

@@ -342,6 +342,32 @@ describe Rubric do
     end
   end
 
+  it "changes workflow state properly when archiving when enhanced_rubrics FF enabled" do
+    course_with_teacher
+    rubric = rubric_model({ context: @course })
+    rubric.archive
+    expect(rubric.workflow_state).to eq "archived"
+  end
+
+  it "changes workflow state propertly when unarchiving when enhanced_rubrics FF enabled" do
+    course_with_teacher
+    rubric = rubric_model({ context: @course })
+    rubric.archive
+    expect(rubric.workflow_state).to eq "archived"
+    rubric.unarchive
+    expect(rubric.workflow_state).to eq "active"
+  end
+
+  it "does not change workflow state when archiving when enhanced_rubrics FF disabled" do
+    # remove this test when FF is removed
+    Account.site_admin.disable_feature!(:enhanced_rubrics)
+    course_with_teacher
+    rubric = rubric_model({ context: @course })
+    rubric.archive
+    expect(rubric.workflow_state).to eq "active"
+    Account.site_admin.enable_feature!(:enhanced_rubrics)
+  end
+
   it "is cool about duplicate titles" do
     course_with_teacher