Move app data back into body

[hannachen]

What this PR does

Follow-up to #1247

An unintentional side-effect was introduced while cleaning up .erb templates. Moving app information from the body to a <script> tag violates the unsafe-inline Content Security Policy.

Reviewer's guide to testing

1. Clone this branch
2. In a terminal, use Shopify CLI to create and configure a new rails app: shopify app create rails
3. Using a text editor, open the Gemfile inside the newly created app
4. Modify the entry of shopify_app to point to this branch in your local environment, it should looks similar to this:
   gem 'shopify_app', path: '~/src/github.com/Shopify/shopify_app'
5. In a terminal, start your app server with shopify app serve, this will also output a ngrok url
6. In a browser, follow the ngrok url to install the app on a test store. It will look similar to this:
   https://1587ef2f72d5.ngrok.io/login?shop=sabotender-shop.myshopify.com
   1. Test 1: On your local environment, remove the shop entry for the store inside the app db (this will simulate one of the cases)
   2. Test 2: Update your generated app scope inside file config/intializers/shopify_app.rb to trigger a redirect from within the shop frame
7. In a browser, open the installed app. i.e. https://sabotender-shop.myshopify.com/admin/apps/test-app-1
8. Ensure that the entire redirect flow takes the browser back to the app.

Things to focus on

1. Focus on install/uninstall
   1. Test 1: Case of a possible incomplete install, where the shop thinks the app is installed, but the app does not have the shop data
   2. Test 2: Case of an app updating access scope, and requires re-auth by breaking out of the shop frame
2. Other areas that might kick off a top level redirect, or use the methods fullpage_redirect_to, authenticate_at_top_level, or enable_cookie_access (Safari browser with strict 3rd party cookie policy)

Checklist

Before submitting the PR, please consider if any of the following are needed:

• Update CHANGELOG.md if the changes would impact users
• Update README.md, if appropriate.
• Update any relevant pages in /docs, if necessary
• For security fixes, the Disclosure Policy must be followed.

[henrytao-me]

🎩-ed. LGTM