Use connection.error_number in MySQLDatabaseTasks

Add a warning for enum elements with 'not_' prefix.

* read config/webpacker.yml to determine which path to exclude for zeitwerk:check

* fix test errors

* more changes to fix test errors

* refactor webpacker_path

[Andrew Kress + Rafael Mendonça França]

In #36560 I accidentally re-introduced a bug where ActiveRecord can't be
used without Rails. This returns an empty hash if we're outside the
context of Rails since we can't create the database tasks without
loading and reading the database yaml which is something only Railties
can do.

Fix index_exists? for PostgreSQL expression indexes

Fix multiple database support for DATABASE_URL env variable

Make ActiveSupport::Logger Fiber-safe

Don't validate non dirty association targets

fix a typo in 5_2_release_notes.md

Fixed db:prepare task to not touch schema when it is disabled

Add support for Proc based parameter filtering on arrays of values

Make currency symbols optional for money column type in PostgreSQL

Add pidfile option to puma config template

Fix host for ActiveStorage DiskService

Fix cache_timestamp_format default value in guides

Exclude missing marshal_dump and _dump methods from being delegated to
an object's delegation target via the delegate_missing_to extension.
This avoids unintentionally adding instance variables to an object
during marshallization, should the delegation target be a method which
would otherwise add them.

In current versions of Ruby, a bug exists in the way objects are
marshalled, allowing for instance variables to be added or removed
during marshallization (see https://bugs.ruby-lang.org/issues/15968).
This results in a corrupted serialized byte stream, causing an object's
instance variables to "leak" into subsequent serialized objects during
demarshallization.

In Rails, this behavior may be triggered when marshalling an object that
uses the delegate_missing_to extension, if the delegation target is a
method which adds or removes instance variables to an object being
marshalled - when calling Marshal.dump(object), Ruby's built in behavior
will check whether the object responds to :marshal_dump or :_dump, which
in turn triggers the delegation target method in the
responds_to_missing? function defined in
activesupport/lib/active_support/core_ext/module/delegation.rb

While future versions of Ruby will resolve this bug by raising a
RuntimeError, the underlying cause of this error may not be readily
apparent when encountered by Rails developers. By excluding marshal_dump
and _dump from being delegated to an object's target, this commit
eliminates a potential cause of unexpected behavior and/or
RuntimeErrors.

Fixes #36522

Move the deprecation call after the new class has been defined:

Assigning to a collection of attachments appends rather than replacing, as in 5.2. Existing 5.2 apps that rely on this behavior will no longer break when they're upgraded to 6.0.

For apps generated on 6.0 or newer, assigning replaces the existing attachments in the collection. #attach should be used to add new attachments to the collection without removing existing ones.

I expect that we'll deprecate the old behavior in 6.1.

Closes #36374.

[ActiveRecord] Deduplicate optimizer hints

Revert "Make UTF-8 string requirement explicit for `ActiveSupport::Inflector.transliterate`"

Make UTF-8 string requirement explicit for `ActiveSupport::Inflector.transliterate`

Fix Loadable.exclude_from to also reset Kernel#require

Fix problem with accessing deprecated constant proxy's subclass

In older Ruby, nil, Symbol, Fixnum, Rational, and Complex were not
duplicable. In Ruby 2.5, all of them are duplicable.

Remove dead code in duplicable.rb

Fix activestorage CI failure due to ffprove version differece

Delete mention of Ruby 1.9 [skip ci]

Prevent exception of loading database yaml with blank config file

Most of this section was written from the time that render file: was the
default, before CVE-2016-0752.

This updates the guide to the Rails 6 `render file:` behaviour, moves it
to a more appropriate part of the file.

[ci skip]

Most of these examples no longer work. The ability to render an absolute
path was removed as part of CVE-2016-0752. In Rails 6 we changed `render
file:` to only take exact paths and always to render them as raw files.
Rendering a template with its extensions _is_ supported, but I don't
think should be recommended.

This also removes `render file:` from an example where it isn't
relevant.

[ci skip]

All this has been simplified.