bookmark api: handle string position, fixes CNVS-20628

test plan:
  * POST this body to /ap/v1/users/self/bookmarks

{"name": "Grades List", "url": "/courses/833052/grades", "position": "0"}

  * verify that the creation succeeds and sets position to 0

Change-Id: I8504d16c110fd7fefd5796861efaf6a951045e92
Reviewed-on: https://gerrit.instructure.com/54695
Tested-by: Jenkins
Reviewed-by: Jacob Fugal <jacob@instructure.com>
QA-Review: August Thornton <august@instructure.com>
Product-Review: Braden Anderson <braden@instructure.com>

app/controllers/bookmarks/bookmarks_controller.rb

@@ -5,6 +5,10 @@
 #       "id": "Bookmark",
 #       "description": "",
 #       "properties": {
+#         "id": {
+#           "example": 1,
+#           "type": "integer"
+#         },
 #         "name": {
 #           "example": "Biology 101",
 #           "type": "string"
@@ -148,7 +152,7 @@ class Bookmarks::BookmarksController < ApplicationController
   end
 
   def set_position
-    params[:position] ? @bookmark.insert_at(params[:position]) : true
+    params[:position] ? @bookmark.insert_at(params[:position].to_i) : true
   end
 
   def render_errors

spec/controllers/bookmarks/bookmarks_controller_spec.rb

@@ -10,7 +10,7 @@ describe Bookmarks::BookmarksController do
 
   context "when user is logged in" do
     let(:u) { user }
-    let(:bookmark) { Bookmarks::Bookmark.create(user_id: u.id, name: 'bio 101', url: '/courses/1') }
+    let!(:bookmark) { Bookmarks::Bookmark.create(user_id: u.id, name: 'bio 101', url: '/courses/1') }
 
     before(:each) do
       user_session(u)
@@ -67,16 +67,19 @@ describe Bookmarks::BookmarksController do
       end
 
       it "should append by default" do
-        bookmark
         post 'create', params
         expect(Bookmarks::Bookmark.order(:id).last).to be_last
       end
 
       it "should set position" do
-        bookmark
         post 'create', params.merge(position: 1)
         expect(Bookmarks::Bookmark.order(:id).last).to_not be_last
       end
+
+      it "should handle position strings" do
+        post 'create', params.merge(position: "1")
+        expect(Bookmarks::Bookmark.order(:id).last).to_not be_last
+      end
     end
 
     describe "PUT 'update'" do