Enable annotations for submission api preview_urls

Test plan:
Make sure submission api results containing preview urls, have
annotations enabled

Fixes RD-4298
Change-Id: Id5358fc82bca6f94cc50f167cc33e7fe6515066f
Reviewed-on: https://gerrit.instructure.com/118357
Tested-by: Jenkins
Reviewed-by: Josh Orr <jgorr@instructure.com>
QA-Review: Mark McDermott <mmcdermott@instructure.com>
Product-Review: Brad Horrocks <bhorrocks@instructure.com>

lib/api/v1/attachment.rb

@@ -109,7 +109,7 @@ module Api::V1::Attachment
     end
     if includes.include? 'preview_url'
       hash['preview_url'] = attachment.crocodoc_url(user, options[:crocodoc_ids]) ||
-                            attachment.canvadoc_url(user)
+                            attachment.canvadoc_url(user, enable_annotations: options[:enable_annotations])
     end
     if includes.include? 'enhanced_preview_url'
       hash['preview_url'] = context_url(attachment.context, :context_file_file_preview_url, attachment, annotate: 0)

lib/api/v1/submission.rb

@@ -162,6 +162,7 @@ module Api::V1::Submission
         atjson = attachment_json(attachment, user, {},
                                  submission_attachment: true,
                                  include: ['preview_url'],
+                                 enable_annotations: true, # we want annotations on submission's attachment preview_urls
                                  crocodoc_ids: attempt.crocodoc_whitelist)
         attachment.skip_submission_attachment_lock_checks = false
         atjson