Ruby 2.7 warning: creating a Proc without a block

Not needed. Since rails-html-sanitizer 1.2.0 removes the needless
deprecations.

This reverts commit 2cd4bce8.

- The sanitizer has been changed to safe_list_sanitizer.

The DATABASE_URL shouldn't change other environments when loaded. This
test verifies this behavior.
Co-Authored-By: NJohn Crepezzi <seejohnrun@github.com>

Fix index_exists? for PostgreSQL expression indexes

Make ActiveSupport::Logger Fiber-safe

Don't validate non dirty association targets

Add pidfile option to puma config template

Port caching documentation fix to stable-5.2

Fix host for ActiveStorage DiskService

Merge pull request #36647 from giraffate/fix_exists_with_distinct_and_offset_and_order_in_postgresql

Fix `relation.exists?` with giving `distinct`, `offset` and `order` for joined table

Fix query cache when using shared connections

PostgreSQL: Fix GROUP BY with ORDER BY virtual count attribute

This is also resolved in `arel_column`.

Fix sqlite3 collation parsing when using decimal columns.

Fix programmatic clicks with data-remote

[ci skip] Use default path in button_to documentation

* Make ActiveRecord `ConnectionPool.connections` thread-safe.

ConnectionPool documentation is clear on the need to synchronize
access to @connections but also states that public methods do not
require synchronization. Existing code exposed @connections
directly via attr_reader. The fix uses synchronize() to lock
@connections then returns a copy to the caller using Array.dup().

Includes comments on the connections method that thread-safe access
to the connections array does not imply thread-safety of accessing
methods on the actual connections.

Adds a test-case that modifies the pool using a supported method
in one thread  while a second thread accesses pool.connections.
The test fails without this patch.

Fixes #36465.

* Update activerecord/test/cases/connection_pool_test.rb

[jeffdoering + Rafael Mendonça França]

images/getting_started: Update screenshot for missing action

Add missing file to require digest/uuid on active_support core ext

When generating a new rails application (rails new) using a custom template that
includes gems from an authenticated source, the user has to provide credentials to
bundler.

One way to do this is by exporting environment variables, for example:

export BUNDLE_GITHUB__COM=user:pass: provides credentials for bundler to fetch
gems from github.com.

The problem this PR addresses is that we are currently scrubs all /BUNDLE_.*/
environment variables by wrapping our system calls in Bundler.with_clean_env.

We do this because we don't want our commands executed against the generated project
to use the generator's bundler environment (e.g. our gems): the generated project should
use it's own configuration.

The problem with Bundler.with_clean_env is that, on top of restoring environment
variables to their original state, it also scrubs any /BUNDLE_.*/ variables, which is harmful for authenticated gem sources.

This PR replaces Bundler.with_clean_env with Bundler.with_original_env, which only
restores environment variables to their initial state, without additional scrubbing.

Fix eager loading associations with string joins not to raise NoMethodError

This fixes a bug that the `foreign_key` and the `foreign_type` are
separated as different table conditions if a polymorphic association has
a scope that joins another tables.

Fix `count(:all)` with eager loading and explicit select and order

https://buildkite.com/rails/rails/builds/61006#c49e1c0d-4c3c-4621-bde5-7cb3cde5ef63

[#35782] Allow loading seeds without ActiveJob (~> 5.2.3)

If executing either `bin/test` in railties or `yarn build` in
actioncable, some build artifacts are left over. The master branch
git ignores those correctly.

However, checking out 5-2-stable means I'll suddenly have to deal with
them. Let's just ignore those artifacts here too.

Proof:

```
kaspth@kaspth-imac:~/code/rails (5-2-stable)$ git status
On branch 5-2-stable
Your branch is up to date with 'origin/5-2-stable'.

Untracked files:
  (use "git add <file>..." to include in what will be committed)

        actioncable/app/javascript/
        railties/test/isolation/assets/
        tmp/
```

mounted routes with non-word characters

Only override async adapter when seeding

Use `googleauth` gem 0.8.0 if Ruby version is 2.2

`googleauth` 0.8.1 requires Ruby 2.3 to support indented here document `<<~`

https://travis-ci.org/rails/rails/jobs/512320216#L1788

```ruby
/home/travis/build/rails/rails/activesupport/lib/active_support/dependencies.rb:291:in `require': /home/travis/.rvm/gems/ruby-2.2.10/gems/googleauth-0.8.1/lib/googleauth/application_default.rb:37: syntax error, unexpected << (SyntaxError)
    NOT_FOUND_ERROR = <<~ERROR_MESSAGE.freeze
```

If Ruby version is 2.3+, we do not have to specify the `googleauth`
gem version because `google-cloud-storage` and `google-api-client` gem
will find the required `googleauth` gem version by itself.

Fix callbacks on has_many :through associations

Type cast falsy boolean symbols on boolean attribute as false

Update CHANGELOG entry for the Cache-Control header change [ci skip]