Merge pull request #14768 from spectator/ac_metal_docfix

Update AC::Metal documentation example
Object#duplicable?
1. Improve tests
2. Remove unnecessary constant
3. Add docs for BigDecimal#duplicable?
Merge pull request #14733 from akshay-vishnoi/test-cases

Improve tests for duplicable, remove unnecessary constant
[ci skip] Avoid suggesting dangerous code in i18n guide

Calling `to_sym` on user input opens apps up to Denial of Service attacks, via the symbol table being expanded to consume vast swathes of memory.

It is a fairly common configuration to have DNS configured such that all subdomains route to your Rails app, in which case an attacker visits `www1.foo.com`, `www2.foo.com`, and so on until something gives.

It is far less likely to have this problem with TLDs, so that change was only for consistency.
Merge pull request #14770 from crazymykl/avoid_dos_vuln_in_i18n_guide

Avoid suggesting dangerous code in i18n guide
SQL Like escaping helper method. [Rob Gilson & Yves Senn]

Closes #14222.

This is a follow up to #6104

This does not have the backwards compatibility issues brought up in
implementation to break.
Changed the NullRelation so that when count is called with #group it will properly return an empty hash instead of zero. Fixes issue #14721

Conflicts:
	activerecord/CHANGELOG.md
Merge pull request #11836 from mcfiredrill/engines-testing-doc

additional note about routes in functional tests for engines [ci skip]
`sanitize_sql_like` escapes `escape_character` not only backslash.

* This is a follow up to: fe4b0eee05f59831e1468ed50f55fbad0ce11e1d
* The originating PR is #14222
* It should fix the build
Merge pull request #14773 from eric-chahin/null_relation_fix

Changed the NullRelation so that when count is called with #group it wil...
[skip ci] Reorder i18n guide

Currently, the section called "How to store your custom translations"
has several subheadings that make no sense, such as "Translations for
ActiveRecord models." These make more sense under the "Overview of the
I18n API Features" section. I moved the "How to store..." section down
to the more appropriate sub-headings "Using Different Backends" and
"Using Different Exception Handlers" and removed the "Customize your
i18n setup" header.
[ci skip] Added examples for color_field_tag method
Merge pull request #14771 from heironimus/i18n_guide_reorder

Reorder i18n guide
Merge pull request #14779 from zenati/master

[ci skip] Added examples for color_field_tag method
[ci skip] Added examples for search_field_tag method
Merge pull request #14780 from zenati/master

[ci skip] Added examples for search_field_tag method
[ci skip] Added examples for telephone_field_tag method
[ci skip] Added examples for url_field_tag method
Merge pull request #14781 from zenati/master

[ci skip] Added examples for telephone_field_tag and url_field_tag methods
Autoload ActiveModel::StrictValidationFailed

Currently, if environment doesn’t eager load code, invoking this
constant before calling #valid? on a model instance results in a
NameError.