`#reset_counters` verifies counter names.

Closes #9724.

Raise an `ArgumentError` when the name of the counter does not
match an association name.

Rework headers functional tests

The env hash passed to `Http::Headers#new` must be in env format.
Also be aware that the passed hash is modified directly.

docs and test-cases for setting headers/env in functional tests.

Follow up to #9700.

Brought up in https://github.com/rails/rails/issues/9727

This reverts commit abba61e2.

Handle conditional get in live requests

Handle conditional get in live requests - this will prevent error when using stale on live streams(issue #9636)

MOAR cleanups of unused variables. 

Even though I read it carefully, my brain tricked me. 😢

Add documentation to ActionDispatch::Request

Rails 4 upgrade notes about clashing named route selection changes

Add support for generate scaffold password:digest

* adds password_digest attribute to the migration
* adds has_secure_password to the model
* adds password and password_confirmation password_fields to _form.html
* omits password from index.html and show.html
* adds password and password_confirmation to the controller
* adds unencrypted password and password_confirmation to the controller test
* adds encrypted password_digest to the fixture

* adds password_digest attribute to the migration
* adds has_secure_password to the model
* adds password and password_confirmation password_fields to _form.html
* omits password entirely from index.html and show.html
* adds password and password_confirmation to the controller
* adds unencrypted password and password_confirmation to the controller test
* adds encrypted password_digest to the fixture

rework passing headers and env variables in integration tests

Closes #6513.

Also:
cleanup, use consistent syntax for `Http::Header` and test.

Change from each to each_value in http/parameters since we don't use key

fix typo in Active Record CHANGELOG [ci skip]