By changing ActionController::Parameter's superclass, Rails 5 also changed
the YAML serialization format.

Since YAML doesn't know how to handle parameters it would fallback to its
routine for the superclass, which in Rails 4.2 was Hash while just Object
in Rails 5. As evident in the tags YAML would spit out:

4.2: !ruby/hash-with-ivars:ActionController::Parameters
5.0: !ruby/object:ActionController::Parameters

Thus when loading parameters YAML from 4.2 in Rails 5, it would parse a
hash dump as it would an Object class.

To fix this we have to provide our own `init_with` to be aware of the past
format as well as the new one. Then we add a `load_tags` mapping, such that
when the YAML parser sees `!ruby/hash-with-ivars:ActionController::Parameters`,
it knows to call our `init_with` function and not try to instantiate it as
a normal hash subclass.

Remove unnecessary methods for `NullRelation`

remove unnecessary require and extend

Suppress warnings

remove old links from debugging guide [ci skip]

`rack/test` is require at the top of file.
https://github.com/rails/rails/blob/master/railties/test/railties/engine_test.rb#L3

In addtion, `Rack::Test::Methods` is include in class, extend is unnecessary.
https://github.com/rails/rails/blob/master/railties/test/railties/engine_test.rb#L9

This commit suppressed
`warning: instance variable @session_store not initialized`.
e5a6f7ee introduced these
warnings.

Revert "Adds `not_in?` onto Object"

Reset rack.input when the environment is scrubbed for the next request

`FinderMethods` uses `records` (`load_target`) when `loaded?` is true

Fix to `CollectionProxy#load` does `load_target`

Remove `prepare_binds_for_database` internal method

Prevent `table_comment` query if a table doesn't have a comment

Avoid calling `current_database` in `table_comment`

`@quoted_{column,table}_names` should cache a frozen string

`current_database` executes a query and `table_comment` is called to all
tables even if a table does not have a comment. Using `current_database`
increases extra queries.

Caching a mutable string causes the following issue.

```
Loading development environment (Rails 5.1.0.alpha)
irb(main):001:0> ActiveRecord::Base.connection.quote_table_name('foo') << '!!'
=> "`foo`!!"
irb(main):002:0> ActiveRecord::Base.connection.quote_table_name('foo') << '!!'
=> "`foo`!!!!"
irb(main):003:0> ActiveRecord::Base.connection.quote_table_name('foo') << '!!'
=> "`foo`!!!!!!"
```

To avoid relying on the connection adapter for type casting binds.

[ci skip] Add documentation for error using select with order

Fix accessing provider_job_id inside active jobs for sidekiq adapter

Updated getting_started.md guide source text to reflect the change in error message …

See https://github.com/nex3/rb-inotify/pull/49

Correctly return `associated_table` when `associated_with?` is true

[Rafael Mendonça França + Takeshi AKIMA]

Remove circular join references in join_dependency

Add rationale for checking auth_tag length for AEAD ciphers

Fix keyed defaults with root

Decouple statement cache from connection adapter

Fixes #25653.

Updated getting_started guide to reflect the change in error message for ActionController::UnknownFromat in ArticlesController#new

Restored texts about XML and JS template handlers. [ci skip]

Before this change, posted parameters would leak across requests. The included
test case failed like so:

      1) Failure:
    TestCaseTest#test_multiple_mixed_method_process_should_scrub_rack_input:
    --- expected
    +++ actual
    @@ -1 +1 @@
    -{"bar"=>"an bar", "controller"=>"test_case_test/test", "action"=>"test_params"}
    +{"foo"=>"an foo", "bar"=>"an bar", "controller"=>"test_case_test/test", "action"=>"test_params"}

An argument could be made that this situation isn't encountered often and that
one should limit the number of requests per test case, but I still think the
parameter leaking is an unexpected side-effect.