Add supports_grade_by_question to assignment type

flag=platform_service_speedgrader
refs EVAL-4291

Test Plan:
- should be able to query supportsGradeByQuestion
   on assignments using graphiql

Change-Id: Icdc6aa286d8e44980cdd570c826adfa24fd0c1eb
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/354453
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Spencer Olson <solson@instructure.com>
QA-Review: Drake Harper <drake.harper@instructure.com>
Product-Review: Drake Harper <drake.harper@instructure.com>

app/graphql/types/assignment_type.rb

@@ -327,6 +327,8 @@ module Types
       load_association(:quiz)
     end
 
+    field :supports_grade_by_question, Boolean, method: :supports_grade_by_question?, null: false
+
     field :discussion, Types::DiscussionType, null: true
     def discussion
       load_association(:discussion_topic)

spec/graphql/types/assignment_type_spec.rb

@@ -993,4 +993,15 @@ describe Types::AssignmentType do
       end
     end
   end
+
+  describe "supportsGradeByQuestion" do
+    it "returns false when the assignment does not support grade by question" do
+      expect(assignment_type.resolve("supportsGradeByQuestion")).to be false
+    end
+
+    it "returns true when the assignment supports grade by question" do
+      assignment.update!(submission_types: "online_quiz")
+      expect(assignment_type.resolve("supportsGradeByQuestion")).to be true
+    end
+  end
 end