fix!: fix course detail page url bug

fix course detail page url as after creating a course, its detail page was not accessible and showing nothing, its url was mismatching and it is fixed by adding the trailing slash "/" to the url

ecommerce/static/js/models/course_model.js

@@ -31,6 +31,9 @@ define([
 
         return Backbone.RelationalModel.extend({
             urlRoot: '/api/v2/courses/',
+            url: function() {
+                return Backbone.Model.prototype.url.call(this) + '/';
+            },
 
             defaults: {
                 id: null,