Adding the `each` method is required for ensuring compatibility between
Rails, and other Rack frameworks (like Sinatra, etc.), that are mounted
within Rails, and wish to use its session tooling. Prior to this, there
was an inconsistency between ActionDispatch::Request::Session and
Rack::Session::Cookie, due to the absence of the `each` method. This
should hopefully fix that error. :)

For a full integration test with Sinatra and a standalone Rack
application, you can check out the gist for that here: https://gist.github.com/maclover7/08cd95b0bfe259465314311941326470.

Solves #15843.

This reverts commit 22db455d, reversing
changes made to 40be61df.

This finishes off what I meant to do in 6216a092.

This reverts commit 45a75a3f.

HWIAs are better than silently deeply-stringified hashes... but that's a
reaction to a shortcoming of one particular session store: we should not
break the basic behaviour of other, more featureful, session stores in
the process.

Fixes #23884

We want to get rid of the `Live::Response` so we are consolidating methods
from `Live::Response` and `Response` by merging them together.

This adds an `#empty` method to the request so we don't need to
hard-code the empty array each time we call an empty
`ActionDispatch::Request`.

The work here is a continuation on combining controller and integration
test code bases into one.

converts old ID methods to the new abstract store methods in Rack

This commit allows us to use one request object rather than allocating
multiple request objects to deal with the session.

Adding tests for Session `destroy`, `update` and `delete` methods. No changes for code under test.

Session#fetch was mutating the session when given a default argument
and/or a block. Since Session duck-types as a Hash, it should behave
like one in these cases.

Mention it in the changelog and add a test checking for regressions.

Hash#fetch isn't adding the defaultly returned value.
However, in the session, saving it is the behavior we should expect.

See discussion in #12692