Since all controller instances are required to have a request and
response object, RackDelegation is no longer needed (we always have to
delegate to the response)

the subclass sets the body on the response object, so we don't need the
superclass doing it too

without this module, the content type is not set correctly

Removed duplicate require 'minitest/mock'

Now that `Controller#status=` just delegates to the response object,
we don't need to set the response on the controller and the response.
We can just set it in one place.

we always have a response object, so there is no reason to test it

these ivars don't exist anymore, so we can remove them from the list

since the controller always has a request on it, we can just ask the
request for the content type.

The controller instance always has an instance of a response object.  We
should store the status code on the response object so that it's only
store in one place.

We always have a response object in controller instances, so we can
remove this conditional

controller instances always have a response object, so we don't need to
test to see if there is one, just always call to_a on the response.

Removed duplicate requires

Use `ActiveRecord::Migration#connection` instead of `@connection`

Fix the unused variable warning

This fixes the following warning.

```ruby
warning: assigned but unused variable - index_definition
```

Fixed to_datetime docs [ci skip]

Controllers should always have a request and response when responding.
Since we make this The Rule(tm), then controllers don't need to be
somewhere in limbo between "asking a response object for a rack
response" or "I, myself contain a rack response".  This duality leads to
conditionals spread through the codebase that we can delete:

  * https://github.com/rails/rails/blob/85a78d9358aa728298cd020cdc842b55c16f9549/actionpack/lib/action_controller/metal.rb#L221-L223

collect the body and make assert against the collected body

we don't need an instance to figure out what type of response to
allocate.  Later we'll pull this up the stack and pass the response
object down

This saves a lambda and request allocation on each request.

controllers should always go through the `action` class method so that
their middleware is respected.

now the caller can just treat it like a regular controller even though
it will return a 404

Removed mocha from Active Record Part 1

Get rid of mocha tests in actionpack - part 2

Initial implementation of ActiveJob AsyncAdapter.

Added docs for TimeWithZone [ci skip]

discard xml Serialization documentation that is no longer available […

Remove unused requires

Remove more unused block arguments

They are already required in `actionpack/lib/action_dispatch.rb` (L25-L26)