return results from multiple shards in enrollments API

test plan:
 - have a student who is enrolled in courses in multiple shards
 - as another user who has permission to view the student's
   enrollments in all shards (i.e., a site admin user, or
   a user with a UserObserver link with the student),
   call /api/v1/users/X/enrollments and verify enrollments
   in all shards are returned

fixes ADMIN-1476

Change-Id: I4b73a7b1f3870f647e968c4b88484d8404402f08
Reviewed-on: https://gerrit.instructure.com/166081
Tested-by: Jenkins
Reviewed-by: Jon Willesen <[email protected]>
QA-Review: Mysti Sadler <[email protected]>
Product-Review: Jeremy Stanley <[email protected]>

app/controllers/enrollments_api_controller.rb

@@ -877,7 +877,7 @@ def user_index_enrollments
       is_approved_parent = user.grants_right?(@current_user, :read_as_parent)
       # otherwise check for read_roster rights on all of the requested
       # user's accounts
-      approved_accounts = user.associated_root_accounts.inject([]) do |accounts, ra|
+      approved_accounts = user.associated_root_accounts.shard(user).inject([]) do |accounts, ra|
         accounts << ra.id if is_approved_parent || ra.grants_right?(@current_user, session, :read_roster)
         accounts
       end

spec/apis/v1/enrollments_api_spec.rb

@@ -1758,7 +1758,7 @@
       end
 
       context "when scoped by a user" do
-        it "returns enrollments from all of a user's associated shards" do
+        it "returns enrollments from all of the current user's associated shards" do
           # create a user on a different shard
           @shard1.activate { @user = User.create!(name: 'outofshard') }
 
@@ -1774,6 +1774,21 @@
           expect(json.first['course_id']).to eq(@course.id)
           expect(json.first['user_id']).to eq(@user.global_id)
         end
+
+        it "returns enrollments from all of another user's associated shards" do
+          @shard1.activate { @other_course = Course.create! account: Account.create! }
+          @course.enroll_student(@user, enrollment_state: 'active')
+          @other_course.enroll_student(@user, enrollment_state: 'active')
+          @student = @user
+          @observer = user_factory
+          @student.linked_observers << @observer
+          json = api_call_as_user(@observer, :get, "/api/v1/users/#{@student.id}/enrollments",
+                          { :controller => "enrollments_api", :action => "index", :user_id => @student.to_param,
+                            :format => "json" })
+          courses = json.map { |el| el['course_id'] }
+          expect(courses).to include @course.id
+          expect(courses).to include @other_course.id
+        end
       end
     end