add users crocodoc id if they have one

refs: RD-4044

Test plan:
Make sure you can still do annotations in canvadocs

Change-Id: Ifc81de7845b4a8ef00b18922768c30c1286bec1c
Reviewed-on: https://gerrit.instructure.com/113099
Reviewed-by: Brad Humphrey <brad@instructure.com>
Tested-by: Jenkins
Product-Review: Caleb Guanzon <cguanzon@instructure.com>
QA-Review: Caleb Guanzon <cguanzon@instructure.com>

lib/canvadocs/session.rb

@@ -36,6 +36,10 @@ module Canvadocs
         user_filter: user.global_id.to_s,
       }
 
+      if user.crocodoc_id != nil
+        opts[:user_crocodoc_id] = user.crocodoc_id
+      end
+
       return opts if submissions.empty?
 
       if submissions.any? { |s| s.grants_right? user, :read_grade }

spec/models/canvadoc_spec.rb

@@ -93,6 +93,16 @@ describe 'Canvadoc' do
       expect(canvadocs_api).to receive(:session).with(anything, hash_including(annotation_context: 'default-super-secret-testing')).and_call_original
       @doc.session_url(user: @attachment.user)
     end
+
+    it "Session creation sends users crocodoc id" do
+      @doc.upload
+      @doc.has_annotations = true
+      @attachment.user.crocodoc_id = 6
+      canvadocs_api = @doc.send(:canvadocs_api)
+
+      expect(canvadocs_api).to receive(:session).with(anything, hash_including(user_crocodoc_id: @attachment.user.crocodoc_id)).and_call_original
+      @doc.session_url(user: @attachment.user)
+    end
   end
 
   describe "#available?" do