fix email regex example code [ci skip]

different from the regex in EmailValidator

Fix ActiveRecord::Callbacks sample code [ci skip]

Callback caller class uses `after_initialize`,
but Callback callee defines `after_find`.

Current sample code causes following error.

  NoMethodError: undefined method `after_initialize' for #<EncryptionWrapper:0x007fe4931fa5c0>

Fix QueryCache to work with nested blocks

This commit takes into account the last cache_enabled value, before clearing query_cache.

Introduce a context for rendering fixtures ERB.

Fixture files are passed through an ERB renderer before being read as
YAML. The rendering is currently done in the context of the main object,
so method definitons leak into other fixtures, and there is no clean
place to define fixture helpers.

After this commit, the ERB renderer will use a new subclass of
ActiveRecord::FixtureSet.context_class each time a fixture is rendered.

Conflicts:
	actionpack/CHANGELOG.md

This PR fixes #13064 regression bug introduced by the #8085

Now in _process_format when the format is a Mime::NullType nothing is written in self.content_type.
In this way the method Response#assign_default_content_type_and_charset can
write the the default mime_type.

Modify the Hash#assert_valid_keys error message so that it shows the valid keys. Also, show the wrong value as it was entered.

{ :failore => "stuff", :funny => "business" }.assert_valid_keys([ :failure, :funny ])
=> ArgumentError: Unknown key: failore
{ 'failore' => "stuff", :funny => "business" }.assert_valid_keys([ :failure, :funny ])
=> ArgumentError: Unknown key: failore

{ 'failore' => "stuff", :funny => "business" }.assert_valid_keys([ :failure, :funny ])
=> ArgumentError: Unknown key: "failore". Valid keys are: :failure, :funny

{ :failore => "stuff", :funny => "business" }.assert_valid_keys([ :failure, :funny ])
=> ArgumentError: Unknown key: :failore. Valid keys are: :failure, :funny

Conflicts:
	activerecord/CHANGELOG.md

Closes #11624.

CHANGELOG for JSON refactor + added back the `encode_big_decimal_as_string` option with warning

Also added the missing CHANGELOG entry for #12183 @ 80e75520 and
4d02296c.

Use the already existing strings instead of creating a new one each time
just to test if it responds to the methods.

Add regression test for IpSpoofAttackError issue

Closes #10780

Refactor and clean up number helpers

Conflicts:
	activesupport/lib/active_support/number_helper.rb

Remove deprecated cattr_* requires

Also wrap surrounding text to 80 chars.

[ci skip] Closes #13132

Unify cattr and mattr accessors declarations

[ci skip]

[ci skip]

[ci skip]

Conflicts:
	guides/source/4_1_release_notes.md

We need to fix this test