Active Admin v3 can be used with the vite_rails gem, but the
instructions for doing so are buried in a discussion comment.

Also, using a modern build system like Vite will often lead to
deprecation warnings due to the older color functions used in Active
Admin's SCSS assets.

To address these issues, I've made some small improvements to Active
Admin's docs. Namely:

- Add a vite_rails section to the installation document.
- Mention the SCSS deprecation warnings in the "gotchas" document, with
  a workaround that specifically works with Vite.

As discussed in
<#8492>, it would
be great to solve the deprecation warnings rather than just hiding them,
but that will require some significant refactoring, which can be a
separate PR. In the meantime I wanted to improve the documentation to at
least point users in the right direction.

…w record form items (#8551)

Fix has_many custom attrs not being set on new record form items

* backport 8500: test against rails 8.0

* Update dependencies

- Downgrade zeitwerk to allow 3.1
- Use Ruby 3.0 to update Rails 7.0 and 7.1 dependencies

```
BUNDLE_GEMFILE=gemfiles/rails_70/Gemfile rvm use 3.0.7 do bash -c "bundle update && bundle update --bundler"
BUNDLE_GEMFILE=gemfiles/rails_71/Gemfile rvm use 3.0.7 do bash -c "bundle update && bundle update --bundler"
```

* Use Struct instead of OpenStruct

---------

Co-authored-by: Geremia Taglialatela <tagliala.dev@gmail.com>

Fix deprecation warning in Ruby 3.4 (#8593)

After upgrade to Ruby 3.4, our test suite outputs the following warning:

```
lib/active_admin/inputs/filters/select_input.rb:19: warning: string returned by <Symbol>.to_s will be frozen in the future
```

Co-authored-by: Yvan BARTHÉLEMY <223016+ybart@users.noreply.github.com>

Fix circular require warning in belongs_to.rb

When running specs with `RUBYOPTS='-w'`, numerous warnings are generated
due to a circular require between:
- `lib/active_admin/resource/belongs_to.rb`
- `lib/active_admin/resource.rb`

The warning message is:

```
warning: loading in progress, circular require considered harmful - ./lib/active_admin/resource.rb

```

Based on the code history, there is no specific reason for the inverse
require from `belongs_to` to `resource`.

This change removes the unnecessary require to eliminate the warnings.

Backports #8598 to `3-0-stable` branch

Update dependencies and test against Ruby 3.4

Additionally, in order to allow CI to run against all supported
Ruby versions:
  - Lock net-imap to ~> 0.4.18 on Rails 6.1
  - Lock nokogiri to ~> 1.17.2 on Rails 6.1 and Rails 7.0
  - Lock securerandom to ~> 0.3.2 on Rails 6.1 and Rails 7.0
  - Do not test Rails 7.1 against Ruby 3.0, change it to the oldest
    supported Rails version, 6.1

bump net-smtp to 0.5.1

Support sortable argument in id_column

This is mostly useful to prevent sorting on tables with uuid PKs.

Sorting by uuid isn't very useful, and it can have problematic performance if the table is very large, even if there is an index.

Backport #8639

support title for id_column