This is a first draft only, needs polishing for final.

Make "bin/setup" works when using PostgreSQL with locales other than en locale

update example url for add_source

[ci skip]

Fix indentation 💇‍♀️

[ci skip]

Ref https://github.com/rails/rails/pull/36621#discussion_r301208961

http://code.whytheluckystiff.net is now just a spam site. Use http://gems.github.com as an example instead.

Add database_exists? method to connection adapters

When DATABASE_URL is specified don't trample envs that use a url: key

fixes #36610

Do not use aliases in GROUP BY clause

Fixes that file attachments without captions would not be represented in plain text generated from rich-text content, causing ActionText::RichText#present? to return false.

Closes #36607.

It is for agnostic test case, since quoted table name may include `.`
for all adapters, and `[` / `]` for sqlserver adapter.

It appears that Oracle does not allow using aliases in GROUP BY clause
unlike ORDER BY clause.

Fixes #36613.

The PostgreSQL adapter uses an error message to determine if a database
exists or not.
https://github.com/rails/rails/blob/74ef67b16de67d2ae2f996e50a18a93aebf68fe6/activerecord/lib/active_record/connection_adapters/postgresql_adapter.rb#L49

However, this message is properly converted according to the locale.
So this check does not work correctly for non-en locales.

As a result, `db:prepare` cannot correctly determine if a database exists, and
`bin/setup`, which depends on the task, does not work correctly if the database
does not exist.

It checks to exist if the "does not exist" exists, but that message is also
used in other error messages(e.g. "role does not exist"). So cannot check
correctly also in en locale.
https://github.com/postgres/postgres/blob/master/src/backend/po/ja.po#L10542

It would be fine could check the status, but in my understanding, when a connecting
fails, only the status `CONNECTION_BAD` be used, and it seems that details cannot
be checked.
https://www.postgresql.org/docs/11/libpq-status.html#LIBPQ-PQSTATUS

I fixed to check whether the error message contains a database
name. This is probably not accurate but can check it better now.

Set process title of parallelized test workers

Fix Browser#preload for older Selenium

MySQL: Fix schema dumping `enum` and `set` columns correctly

Update docs on dirty.rb

[ci skip]

`previously_changed` seems to actually be `previous_changes`

`enum` and `set` are typed cast as `:string`, but currently the
`:string` type is incorrectly reused for schema dumping.

A cast type on columns is not always the same with `sql_type`, this
fixes schema dumping `enum` and `set` columns to use `sql_type` instead
of `type` correctly.

Since #36424, we need an newer version in order to pass.

Older versions of selenium had driver_path on
::Selenium::WebDriver::Chrome directly, not on Service. This avoids
errors on those old versions and will preload properly if webdrivers is
installed.

Preload browser driver_path to fix system testing under parallelism

Update docs regarding skipping CI tests [ci skip]

The phrasing of this struck we as odd, "To help our CI servers..." So I
feel it would be more useful if we explain more explicitly that ci skip
cuts down on usage by not running CI.

The webdrivers gem configures Selenium::WebDriver::Service.driver_path
as a proc which updates the web drivers and returns their path.

This commit introduces SystemTesting::Browser#preload, which runs this
proc early. This ensures that webdrivers update is run before forking
for parallel testing, but doesn't explicitly tie us to that gem (and I
think anything configured as driver_path probably makes sense to
eager-load).

Fix swapped replica/primary in multi-db docs [ci skip]

Add the ability to set the CSP nonce only to the specified directives

Replace replica with primary in automatic connection switching after write in multi-db docs [ci skip]

Reads after write should be from the primary database.

This reverts commit 60e19c6d, reversing
changes made to 72e257b4.

The method signature is different between `create_file` and `template`.

https://www.rubydoc.info/github/erikhuda/thor/master/Thor/Actions#create_file-instance_method
https://www.rubydoc.info/github/erikhuda/thor/master/Thor/Actions#template-instance_method

[skip ci] use 'template' instead of 'create_file' for erb templates in generators guide

This version makes eager loading and autoloading consistent,
as documented in the upgrading guide.

This makes to be able to ignore the query in `assert_queries` even if
accidentally reconnected a connection.

https://buildkite.com/rails/rails/builds/61917#4c49187a-3173-4d5c-8a8d-d65768f5bfc9/1000-1799

Introduced in bba7c63a

Before:

```
$ TESTOPTS="-n=/test_yaml_dump_and_load/" bundle exec rake
test:postgresql

:scisors: ... :scisors:

Using postgresql
Run options: -n=/test_yaml_dump_and_load/ --seed 36896

/home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15:
warning: instance variable @serial not initialized
/home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15:
warning: instance variable @serial not initialized
/home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15:
warning: instance variable @serial not initialized
/home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15:
warning: instance variable @serial not initialized
/home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15:
warning: instance variable @serial not initialized
/home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15:
warning: instance variable @serial not initialized
/home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15:
warning: instance variable @serial not initialized
/home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15:
warning: instance variable @serial not initialized
/home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15:
warning: instance variable @serial not initialized
/home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15:
warning: instance variable @serial not initialized
/home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15:
warning: instance variable @serial not initialized
/home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15:
warning: instance variable @serial not initialized
/home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15:
warning: instance variable @serial not initialized
/home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15:
warning: instance variable @serial not initialized
/home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15:
warning: instance variable @serial not initialized
/home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15:
warning: instance variable @serial not initialized
/home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15:
warning: instance variable @serial not initialized
/home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15:
warning: instance variable @serial not initialized
/home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15:
warning: instance variable @serial not initialized
/home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15:
warning: instance variable @serial not initialized
/home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15:
warning: instance variable @serial not initialized
/home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15:
warning: instance variable @serial not initialized
/home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15:
warning: instance variable @serial not initialized
/home/u/code/rails/activerecord/lib/active_record/connection_adapters/postgresql/column.rb:15:
warning: instance variable @serial not initialized
.

Finished in 0.195325s, 5.1197 runs/s, 35.8376 assertions/s.
1 runs, 7 assertions, 0 failures, 0 errors, 0 skips

```
Co-authored-by: NRyuta Kamizono <kamipo@gmail.com>