Overview/summary

I was looking forward to the next release to fix some important but, but I see its been done in a breaking release with some significant session storage changes...

In trying to update, I now get errors about session storage, but the documentation is all unchanged.

1. The current documentation for session_storage appears to be outdated (I think this option no longer exists?)
   

   shopify-api-ruby/README.md

   Line 55 in fca16f1

   session_storage: ShopifyAPI::Auth::FileSessionStorage.new, # See more details below

2. The Setup a Session Store section appears to be outdated and references things that no longer exist.

3. The linked session storage also appears to be outdated. https://github.com/Shopify/shopify-api-ruby/blob/fca16f181f528216a98edf8a4db8c572e2d82e7d/docs/usage/session_storage.md

4. if shopify_app is now required to do sessions, can you document how that works completely? Ideally also including people that just run this as a CLI or script kind of thing as mentioned in Warning about Sessions?? #1084

is shopify_app now a hard dependency? If so, I'd like to see more documentation on that.

Personally, I'm using the shopify gem in a private app to run code just for our store. I don't need anything that shopify_app provides, so for me, this is not a good change. I was perfectly fine using the filesystem based session storage, I'd rather not make a new table and introduce all the session data there for no reason. Is there a way to do that?