add assignment_name to grade_change event

closes PLAT-4968

test plan:
* give a student a grade for an assignment
* configure the live events plugin using `doc/live_events.md`
* tail the kinesis stream following the directions in `doc/live_events.md`
* change the grade for the student
* assert that the assigment_name is present in the event body

Change-Id: Ibcabdada2a1c4ba7cd9b29bc6bacdbb387ec41f1
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/215983
Reviewed-by: Evan Battaglia <ebattaglia@instructure.com>
QA-Review: Evan Battaglia <ebattaglia@instructure.com>
Product-Review: Xander Moffatt <xmoffatt@instructure.com>
Tested-by: Jenkins

doc/api/live_events.md

@@ -313,6 +313,7 @@ these cases, `grader_id` should be null in the body.
 | ----- | ----------- |
 | `submission_id` | The Canvas id of the submission that the grade is changing on. |
 | `assignment_id` | The Canvas id of the assignment associated with the submission. |
+| `assignment_name` | The name of the assignment associated with the submission. |
 | `grade` | The new grade. |
 | `old_grade` | The previous grade, if there was one. |
 | `score` | The new score. |

lib/canvas/live_events.rb

@@ -473,6 +473,7 @@ def self.grade_changed(submission, old_submission=nil, old_assignment=submission
     post_event_stringified('grade_change', {
       submission_id: submission.global_id,
       assignment_id: submission.global_assignment_id,
+      assignment_name: submission.assignment.name,
       grade: submission.grade,
       old_grade: old_submission.try(:grade),
       score: submission.score,

spec/lib/canvas/live_events_spec.rb

@@ -256,6 +256,7 @@ def wiki_page_updated
       expect_event('grade_change', hash_including({
         submission_id: @quiz_submission.submission.global_id.to_s,
         assignment_id: @quiz_submission.submission.global_assignment_id.to_s,
+        assignment_name: @quiz_submission.submission.assignment.name,
         grader_id: nil,
         student_id: @quiz_submission.user.global_id.to_s,
         user_id: @quiz_submission.user.global_id.to_s
@@ -271,6 +272,7 @@ def wiki_page_updated
       expect_event('grade_change', hash_including(
         submission_id: submission.global_id.to_s,
         assignment_id: submission.global_assignment_id.to_s,
+        assignment_name: submission.assignment.name,
         grader_id: @teacher.global_id.to_s,
         student_id: @student.global_id.to_s,
         user_id: @student.global_id.to_s
@@ -289,6 +291,7 @@ def wiki_page_updated
       expect_event('grade_change',
         hash_including({
           assignment_id: submission.global_assignment_id.to_s,
+          assignment_name: submission.assignment.name,
           user_id: @student.global_id.to_s,
           student_id: @student.global_id.to_s,
           student_sis_id: nil