* master: (74 commits)
  [ci skip] builtin -> built-in
  Fix code indentation and improve formatting
  Grammar fix in Getting Started Guide
  Make URL escaping more consistent
  Optimize URI escaping
  Always escape string passed to url helper.
  Remove statement assuming coffee shop/public space wifi is inherently insecure
  Don't rely on Arel master in bug report template [ci skip]
  wrap methods in backticks [ci skip]
  "subhash" --> "sub-hash"
  multibyte_conformance.rb --> multibyte_conformance_test.rb
  Fix inconsistent behavior from String#first/#last
  `@destroyed` should always be set to `false` when an object is duped.
  remove warning `warning: ambiguous first argument; put parentheses or even spaces`
  :uglify -> :uglifier
  Regression test for irregular inflection on has_many
  Singularize association names before camelization
  Fix spelling and proper nouns
  Optimize select_value, select_values, select_rows and dry up checking whether to exec with cache for Postgresql adapter
  Include default rails protect_from_forgery with: :exception
  ...

Conflicts:
	activerecord/lib/active_record/connection_adapters/abstract_mysql_adapter.rb
	activerecord/lib/active_record/connection_adapters/sqlite3_adapter.rb

[ci skip] builtin -> built-in

Fix code indentation and improve formatting

in the Getting Started Guide.

This PR regroups #14817, #14818 and #14819 into one commit.

[skip ci]

Grammar fix in Getting Started Guide [ci skip]

1. Escape '%' characters in URLs - only unescaped data
   should be passed to URL helpers

2. Add an `escape_segment` helper to `Router::Utils`
   that escapes '/' characters

3. Use `escape_segment` rather than `escape_fragment`
   in optimized URL generation

4. Use `escape_segment` rather than `escape_path`
   in URL generation

For point 4 there are two exceptions. Firstly, when a route uses wildcard
segments (e.g. *foo) then we use `escape_path` as the value may contain '/'
characters. This means that wildcard routes can't be optimized. Secondly,
if a `:controller` segment is used in the path then this uses `escape_path`
as the controller may be namespaced.

Fixes #14629, #14636 and #14070.

The URI::Parser#escape method is a general use method that has to deal
with a variety of input however our use of it is limited in scope so
we can increase the performance by implementing our specific needs
within ActionDispatch::Journey::Router::Utils directly.

If there is no encoding required then there is no change in performance
or number of objects allocated, but for each character that needs to be
encoded we save five object allocations and gain a performance boost.
The performance boost seen varies from 20% when there is one character
to over 50% when encoding ten characters.

Makes it clear that anything passed with the helper must not be percent encoded.

Fixes previous behavior which tricks people into believing passing
non-percent-encoded will generate a proper percent-encoded path while in
reality it doesn't ('%' isn't escaped).

The intention is nice but the heuristic is broken.

Remove statement assuming coffee shop/public space wifi is inherently insecure

Don't rely on Arel master in bug report template

We should rely instead on the version supported by Active Record

Closes #14809

multibyte_conformance.rb --> multibyte_conformance_test.rb

"subhash" --> "sub-hash"

Few corrections in Rails Initialization Guides

Fix inconsistent behavior from String#first/#last

While calling String#first or String#last with zero or a Fixnum < the
string's length returns a new string, a Fixnum >= the string's length
returns the string itself. This inconsistency can lead to inadvertent
mutation of a string.

when a destroyed record is duped, it is no longer ´destroyed?`.

remove warning while running TEST CASES

`warning: ambiguous first argument; put parentheses or even spaces`

:uglify -> :uglifier

The name of the gem is `uglifier` and all other references
use `uglifier`, not `uglify`.

Optimize select_value, select_values, select_rows in Postgresql adapter.

Fixed has_many association to make it support irregular inflections.

Also add a Changelog entry

[related #9702]
[fixes #8928]

So that irregular multi-word pluralization rules have to be defined only for snake-case strings.

[ci skip]

CSRF protection should rescue exception not extend

Optimize select_value, select_values, select_rows and dry up checking whether to exec with cache for Postgresql adapter

Reduces creating unused objects, with the most dramatic reduction in select_values which used to map(&:first) an array of single element arrays.

Extend previous changes, include the default line from the application controller that new rails applications are created with: 
  protect_from_forgery with: :exception

Minor wording changes to align.

Related with cbb91745

This was changed at cbb91745