raise ActiveModel::MissingAttributeError when trying to access a relationship without the foreign key attribute

raise ActiveModel::MissingAttributeError when trying to access a relationship without the foreign key attribute

fixes regression reported on #20253

ActiveRecord::Base#[] was not used cause of 8b954200

Small refactor on db:reset

People should be free to mutate the header object, but not to set a new
header object.  That header object may be specific to the webserver, and
we need to hide it's internals.

this way we don't have to mutate the instance (as much) when writing a
rack response

Deprecate passing hash as first parameter into ActionController::Head

Add missing spec and documentation for button_tag helper

 Added test case for serial? method when sequence name is not quoted

Removed not needed includes, As record_tag_helper is moved to a gem we..

Fix flakyness.

Brought on by my own stupidity :)

db:reset should not prematurely load the environment, so, for instance,
if there is any initializer that touches th DB, it will not touch that
before droping it.

Also this makes the code simpler.

This changed was made back in 15fb4302
, not sure why. But I am pretty much sure we should do it like this, as
drop and setup should load its dependencies tasks if necessary.

[ci skip] Fix the Rails::Generators::NamedBase#template doc

Fix the message verifier encoding issue

make sure to load_config for db:abort_if_pending_migrations

Fix inflector test by using dup inflections when it needs to be changed

This is not something that is failing at the moment, but can do it
eventually. I had the issue with db620812 as the HEAD and with the
following change:

```
--- a/activesupport/test/inflector_test.rb
+++ b/activesupport/test/inflector_test.rb
@@ -101,6 +101,7 @@ class InflectorTest < ActiveSupport::TestCase
   def test_acronyms
     ActiveSupport::Inflector.inflections do |inflect|
       inflect.acronym("API")
+      inflect.acronym("HTM")
       inflect.acronym("HTML")
       inflect.acronym("HTTP")
       inflect.acronym("RESTful")
```

I was expecting only `test_acronyms` to fail, but with a specific `seed`
others were also failing: `ruby -w -I"lib:test" test/inflector_test.rb
--seed 4313`.

Now, `inflections` instance is duplicated on `setup` and restored on
`teardown`.

I decided to benchmark and check the impact of the patch and it seems
to me to be fine.

```
Calculating -------------------------------------
     without changes     1.000  i/100ms
      with setup dup     1.000  i/100ms
      with block dup     1.000  i/100ms
-------------------------------------------------
     without changes      0.817  (± 0.0%) i/s -      5.000  in
     6.119916s
      with setup dup      0.784  (± 0.0%) i/s -      4.000
      with block dup      0.797  (± 0.0%) i/s -      4.000
```

Where `with setup dup` duplicates on setup for each test and `with block`
duplicates for just for tests that actually modify `inflections`.

* Fix a few remaining typos
* Wrap lines to 80 chars
* Fix the conversion from Textile to Markdown
* Update the part about `Rack::Cache` which isn't included anymore and
  speak about Active Support's provided middleware
* Remove references to out-of-date methods and middlewares (e.g.
  respond_with) and update the list of modules and middlewares to match
  the actual code-base.
* Remove the middleware's description and links to the Rack guide

[ci skip]

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

This used to raise a `IrreversibleMigration` error (since #10437).
However since `remove_index :table, :column` is probably the most basic
use-case we should make it reversible again.

Conflicts:
	activerecord/CHANGELOG.md

Add RDoc about add_reference to ActiveRecord::Migration

[ci skip]

Updated bundler link [ci skip]

Since #13612, `template` is no longer being used to generate
migrations.

ActionDispatch::SSL should keep original header's behavior

```ruby
verifier = ActiveSupport::MessageVerifier.new('secret')
verifier.verify("\xff") # => ArgumentError: invalid byte sequence in UTF-8
```

 Add missing "header" word in documentation of Token#authentication_request [ci skip]

Wrong documentation about Rails autoload on active_jobs_basics doc [ci skip]

By default Rails automaticaly loads all files under the app directory

`ActionDispatch::SSL` changes headers to `Hash`.
So some headers will be broken if there are some middlewares
on ActionDispatch::SSL and if it uses `Rack::Utils::HeaderHash`.

Add gotcha to RDoc of collection_check_boxes

Extended 'Active Job Basics' guide with more detailed information

[ci skip] fix typo mistake