* Extend image_tag to accept ActiveStorage's Attachments and Variants

* Flip resolve_image_source around

* Add tests for the new use-cases of image_tag

* Remove the higher-level test

* Update image_tag documentation

* Add error states into the test suite

* Re-raise polymorhic_url's NoMethodError as ArgumentError

* delegate_missing_to will raise DelegationError instead of NoMethodError

Should _probably_ be done across the board with all of our
documentation, but going to leave that for another time :)

[ci skip]

[ci skip]

Light grammar edits.

[ci skip]

Light grammar edits.

[ci skip]

Light grammar fixes, and added a few backticks.

[ci skip]

Fixes a few grammar things.

[ci skip]

Postgres --> PostgreSQL
ActionCable --> Action Cable

[ci skip]

Fix wrong service name in the storage.yml

Merge pull request #30099 from bogdanvlviv/set_version_of_active_storage_to_5_2_0_alpha_inside_package_json

Active Storage to 5.2.0.alpha inside `activestorage/package.json`

Follow #30083

Replaces the 17 for the actual call to params[:id] that would make th…

Replaces the 17 for the actual call to params[:id] that would make the code work as intended. [ci skip]

Remove outdated comment [ci skip]

The comment was describing a previous version of the method with
a different signature. This is outdated since e76c38ef

`module ActiveStorage`, not `ActiveStorage::Class`

Use `content_type.start_with?("...")` than `content_type =~ /^.../`

Fix ruby warnings

Active Storage: check for `app.secrets.secret_key_base`, not `app.config.secret_key_base`

Add missing blank line between `config.active_storage` and `config.action_cable`

Change gem version of Active Storage to 5.2.0.alpha

By default, apps only have the former set.

Remove unnecessary variable

It was right as originally written in #15440.

This fixes following warnings:

```
test/models/variant_test.rb:11: warning: ambiguous first argument; put parentheses or a space even after `/' operator
lib/active_storage/attached/macros.rb:63: warning: instance variable @active_storage_attached_highlights not initialized
lib/active_storage/attached/macros.rb:25: warning: instance variable @active_storage_attached_avatar not initialized
```

The reasons for this commit are:

- uniformity with the other Rails libraries
- (possibly) behave better with respect to autoloading
- fix the index in the generated documentation

Before this commit, run `rake rdoc` generates this left sidebar
(ActiveStorage entries are indexed twice, both inside and outside the module):

<img width="308" alt="before" src="https://user-images.githubusercontent.com/10076/28939523-7c087dec-7846-11e7-9289-38ed4a2930cd.png">

After this commit, run `rake rdoc` generates this left sidebar:
(ActiveStorage entries are only indexed inside the module):

<img width="303" alt="after" src="https://user-images.githubusercontent.com/10076/28939524-7c090be0-7846-11e7-8ee5-29dfecae548e.png">

Fix repository URL [ci skip]

changed `rails/activestorage` to `rails/rails`.

`start_with?` is a little faster than regexp for prefix matching by a
fixed string.

Add Active Storage to Rails 

If an AWS bucket name includes a `.` (e.g. `bucket.name`), then the canonical
URL for an object will start with "https://s3.amazonaws.com/bucket.name/"
and not with "https://bucket.name.s3.amazonaws.com/".

The URL tests have now been separated into two separate asserts, to ensure
that both the "s3.amazonaws.com" and the "bucket.name" components are included,
but not specifically in that order.

Before we forget...

Do not let use `serialize` on native JSON/array column