persist the course banner image across content migrations

test plan:
 1. enable K5 mode
 2. set a wide banner image on a course to a file from the course
 3. copy the course
 4. the image should follow
 5. repeat steps 2-4 using an external URL instead of a course file
 6. repeat steps 2-5 only export/import instead of course copy

flag=none
fixes LS-2881

Change-Id: I7184e8a6d77d5b793fbfe3d2a4582ab5df1b00f9
Reviewed-on: https://gerrit.instructure.com/c/canvas-lms/+/280538
Tested-by: Service Cloud Jenkins <svc.cloudjenkins@instructure.com>
Reviewed-by: Ed Schiebel <eschiebel@instructure.com>
QA-Review: Ed Schiebel <eschiebel@instructure.com>
Product-Review: Jeremy Stanley <jeremy@instructure.com>

app/models/importers/course_content_importer.rb

@@ -496,6 +496,14 @@ module Importers
         course.image_id = image_att.id
         course.image_url = nil
       end
+      if (banner_image_url = settings[:banner_image_url])
+        course.banner_image_url = banner_image_url
+        course.banner_image_id = nil
+      elsif (image_ref = settings[:banner_image_identifier_ref]) &&
+            (image_att = course.attachments.where(migration_id: image_ref).active.first)
+        course.banner_image_id = image_att.id
+        course.banner_image_url = nil
+      end
       if settings[:lock_all_announcements]
         Announcement.lock_from_course(course)
       end

lib/cc/canvas_resource.rb

@@ -163,6 +163,14 @@ module CC
           end
         end
 
+        if @course.banner_image_url.present?
+          atts << :banner_image_url
+        elsif @course.banner_image_id.present?
+          if (image_att = @course.attachments.active.where(id: @course.banner_image_id).first)
+            c.banner_image_identifier_ref(create_key(image_att))
+          end
+        end
+
         @course.disable_setting_defaults do # so that we don't copy defaulted settings
           atts.uniq.each do |att|
             c.tag!(att, @course.send(att)) unless @course.send(att).nil? || @course.send(att) == ""

lib/cc/importer/canvas/course_settings.rb

@@ -64,7 +64,8 @@ module CC::Importer::Canvas
          turnitin_comments default_view license locale
          group_weighting_scheme storage_quota grading_standard_identifier_ref
          overridden_course_visibility root_account_uuid
-         image_url image_identifier_ref course_color alt_name].each do |string_type|
+         image_url image_identifier_ref banner_image_url banner_image_identifier_ref
+         course_color alt_name].each do |string_type|
         val = get_node_val(doc, string_type)
         course[string_type] = val unless val.nil?
       end

lib/cc/xsd/cccv1p0.xsd

@@ -105,6 +105,8 @@
         <xs:element name="alt_name" type="xs:string" minOccurs="0"/>
         <xs:element name="image_url" type="xs:string" minOccurs="0"/>
         <xs:element name="image_identifier_ref" type="xs:string" minOccurs="0"/>
+        <xs:element name="banner_image_url" type="xs:string" minOccurs="0"/>
+        <xs:element name="banner_image_identifier_ref" type="xs:string" minOccurs="0"/>
         <xs:element name="default_view" minOccurs="0">
           <xs:simpleType>
             <xs:restriction base="xs:string">

spec/models/content_migration/course_copy_spec.rb

@@ -542,6 +542,28 @@ describe ContentMigration do
       expect(@copy_to.image_url).to eq example_url
     end
 
+    it "copies banner images" do
+      att = attachment_model(context: @copy_from, uploaded_data: stub_png_data, filename: "homework.png")
+      @copy_from.banner_image_id = att.id
+      @copy_from.save!
+
+      run_course_copy
+
+      @copy_to.reload
+      new_att = @copy_to.attachments.where(migration_id: mig_id(att)).first
+      expect(@copy_to.banner_image_id.to_i).to eq new_att.id
+
+      example_url = "example.com"
+      @copy_from.banner_image_url = example_url
+      @copy_from.banner_image_id = nil
+      @copy_from.save!
+
+      run_course_copy
+
+      @copy_to.reload
+      expect(@copy_to.banner_image_url).to eq example_url
+    end
+
     it "converts domains in imported urls if specified in account settings" do
       account = @copy_to.root_account
       account.settings[:default_migration_settings] = { domain_substitution_map: { "http://derp.derp" => "https://derp.derp" } }