Support parents with cross-shard enrollments

closes LS-2750
flag = k5_parent_support

Test plan:
 - Check out the setup steps in ticket LS-2750
 - Visit the dashboard as the observer and expect to see the
   cross-shard user in the dropdown

Change-Id: I9dff318e177e7891a063f4cf4afa860fb38b1280
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/276370
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Nate Armstrong <narmstrong@instructure.com>
QA-Review: Nate Armstrong <narmstrong@instructure.com>
Product-Review: Jackson Howe <jackson.howe@instructure.com>

app/helpers/observer_enrollments_helper.rb

@@ -31,9 +31,9 @@ module ObserverEnrollmentsHelper
   def observed_users(user, session, course_id = nil)
     return [] unless user
 
-    users = Rails.cache.fetch_with_batched_keys(["observed_users", course_id].cache_key, batch_object: user, batched_keys: :enrollments, expires_in: 1.hour) do
+    users = Rails.cache.fetch_with_batched_keys(["observed_users", course_id].cache_key, batch_object: user, batched_keys: :enrollments, expires_in: 1.day) do
       GuardRail.activate(:secondary) do
-        scope = user.enrollments.active_or_pending
+        scope = user.enrollments.active_or_pending.shard(user.in_region_associated_shards)
         scope = scope.where(course_id: course_id) if course_id
         has_own_enrollments = scope.not_of_observer_type.exists?
         users = User.where(

spec/helpers/observer_enrollments_helper_spec.rb

@@ -171,12 +171,15 @@ describe ObserverEnrollmentsHelper do
   context "sharding" do
     specs_require_sharding
 
-    it "includes and sorts observed users from multiple shards" do
+    before :once do
       @shard2.activate do
         @student3 = user_factory(active_all: true, name: "Student 3")
-        @student3.sortable_name = "0" # before student 1
-        @student3.save!
       end
+    end
+
+    it "includes and sorts observed users from multiple shards" do
+      @student3.sortable_name = "0" # before student 1
+      @student3.save!
       @course1.enroll_student(@student3)
       enroll_observer(@course1, @observer, @student3)
       enroll_observer(@course1, @observer, @student1)
@@ -186,5 +189,20 @@ describe ObserverEnrollmentsHelper do
       expect(users[0][:name]).to eq("Student 3")
       expect(users[1][:name]).to eq("Student 1")
     end
+
+    it "includes observers with observer enrollments in courses on another shard" do
+      enroll_observer(@course1, @observer, @student1)
+      @shard2.activate do
+        account = Account.create!
+        @course3 = course_factory(active_all: true, account: account)
+        @course3.enroll_student(@student3)
+        enroll_observer(@course3, @observer, @student3)
+
+        users = observed_users(@observer, nil)
+        expect(users.length).to be(2)
+        expect(users[0][:name]).to eq("Student 1")
+        expect(users[1][:name]).to eq("Student 3")
+      end
+    end
   end
 end