Follow up to  #23434

- Fixes #22876.

It's pretty common for folks to monkey patch `ActiveRecord::Base` to
work around an issue or introduce extra functionality. Instead of
shoving even more stuff in `ActiveRecord::Base`, `ApplicationRecord` can
hold all those custom work the apps may need.

Now, we don't wanna encourage all of the application models to inherit
from `ActiveRecord::Base`, but we can encourage all the models that do,
to inherit from `ApplicationRecord`.

Newly generated applications have `app/models/application_record.rb`
present by default. The model generators are smart enough to recognize
that newly generated models have to inherit from `ApplicationRecord`,
but only if it's present.

[ci skip]

The PostgreSQL 9.4 docs suggest to use `pgcrypto`.
Howerver `create_table id: :uuid` will still default to `uuid_generate_v4()`

From the Postgresql 9.4+ docs

> If you only need randomly-generated (version 4) UUIDs, consider using
  the gen_random_uuid() function from the pgcrypto module instead.

[ci skip]

Add information about usage `uuid` type with `reference`

- Changed `IN` to `ON` in all note sentences in guides.

References #18148.

ref #15674

This is a reaction to https://github.com/rails/rails/commit/7ca75f3789e316b6f3dc1f8000ec4f85c8ba32ea#commitcomment-6303828

Also change Json => JSON.

Fill Ruby's Range & IPAddr link.