Fixes #33083

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The 'setup' section was misleadingly leaving out :bucket and :region in the sample, but servers don't start without them.

Now requires version 1.11 or newer. Ref: bf5f41d9

This line refers only to an upgrade situation, but same is need to setup AST in a new application.

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http links will be redirected to the https version, but still better to
just directly link to the https version.

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It adds a note to the Active Storage documentation regarding the use of Mirror Service not being compatible with the use of the Direct Uploads as described later on in the documentation, as described in issue #32732

Also fix syntax highlighting in the more advanced JS example.

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Avoid the likes of:

```
Error:
ActiveStorage::RepresentationTest#test_representing_an_MP4_video:
Errno::ENOENT: No such file or directory - ffmpeg
    test/models/representation_test.rb:27:in `block in <class:RepresentationTest>'
```

Also note additiona macOS requirements in ActiveStorage guide.

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The prior sentence is referring just to an existing user object, so
the sudden magical 'Current.' prefix doesn't make sense. Remove it.

This adds a boolean argument called identify to ActiveStorage::Blob
methods #create_after_upload, #build_after_upload and #upload. It
allows a user to bypass the automatic content_type inference from
the io.

Fix spelling, grammar, and formatting.

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- added documentation on how to download files, with example of
  ActiveStorage::Downloading
- documentation about linking files outside of controller/view
- added section about DirectUpload JavaScript integration into
  libraries/frameworks, as well as usage in combination with Drag and Drop

ImageProcessing gem is a wrapper around MiniMagick and ruby-vips, and
implements an interface for common image resizing and processing. This
is the canonical image processing gem recommended in [Shrine], and
that's where it developed from. The initial implementation was extracted
from Refile, which also implements on-the-fly transformations.

Some features that ImageProcessing gem adds on top of MiniMagick:

  * resizing macros
    - #resize_to_limit
    - #resize_to_fit
    - #resize_to_fill
    - #resize_and_pad
  * automatic orientation
  * automatic thumbnail sharpening
  * avoids the complex and inefficient MiniMagick::Image class
  * will use "magick" instead of "convert" on ImageMagick 7

However, the biggest feature of the ImageProcessing gem is that it has
an alternative implementation that uses libvips. Libvips is an
alternative to ImageMagick that can process images very rapidly (we've
seen up 10x faster than ImageMagick).

What's great is that the ImageProcessing gem provides the same interface
for both implementations. The macros are named the same, and the libvips
implementation does auto orientation and thumbnail sharpening as well;
only the operations/options specific to ImageMagick/libvips differ. The
integration provided by this PR should work for both implementations.

The plan is to introduce the ImageProcessing backend in Rails 6.0 as the
default backend and deprecate the MiniMagick backend, then in Rails 6.1
remove the MiniMagick backend.

If an explicit AWS key pair and/or region is not provided in
config/storage.yml, attempt to use environment variables, shared
credentials, or IAM role credentials. Order of precedence is
determined by the AWS SDK[1].

[1]: https://docs.aws.amazon.com/sdk-for-ruby/v3/developer-guide/setup-config.html

The Active Storage service for Azure Storage has an option called `path`
that is ambiguous in meaning. It needs to be set to the primary blob
storage endpoint but that can be determined from the blobs client anyway.

To simplify the configuration this commit removes the `path` option and
gets the endpoint from the blobs client instead.

Closes #32225.

Fixes #32129.

Documents ActiveStorage file cleanup in Integration Tests which is
similar but slightly different than the existing docs for System Tests.

Because we use `credentials` in an example of configuration files, but
`credentials` can not be used unless it is 1.8.0 or later.

Ref: 9d65ac30

The [template](https://github.com/rails/rails/blob/master/railties/lib/rails/generators/rails/app/templates/config/storage.yml.tt#L10)
that generates the `config/storage.yml` file has the Amazon S3 key specified as `:amazon`, not `:s3`.

The guides should reflect the nomenclature, given that every other service also
has the name of the company as the key (:google, :microsoft).

Like other Basics and Overview guides.