Fixing  "Adding Member Routes" documentation

Between 4.2 and 5.0 the behavior of how multiparameter attributes
interact with `_before_type_cast` changed. In 4.2 it returns the
post-type-cast value. After 5.0, it returns the hash that gets sent to
the type. This behavior is correct, but will cause an issue if you then
tried to render that value in an input like `text_field` or
`hidden_field`.

In this case, we want those fields to use the post-type-cast form,
instead of the `_before_type_cast` (the main reason it uses
`_before_type_cast` at all is to avoid losing data when casting a
non-numeric string to integer).

I've opted to modify `came_from_user?` rather than introduce a new
method for this as I want to avoid complicating that contract further,
and technically the multiparameter hash didn't come from assignment, it
was constructed internally by AR.

Close #27888.

Add documentation for class_attribute default option

Remove useless `arel_engine`

This change was introduced by #18109. The intent of that change was to
specifically apply `unscoped`, not to allow all changes to
`current_scope` to affect the join. The idea of allowing `current_scope`
to affect joins is interesting and potentially more consistent, but has
sever problems associated with it. The fact that we're specifically
stripping out joins indicates one such problem (and potentially leads to
invalid queries).

Ultimately it's difficult to reason about what `Posts.joins(:users)`
actually means if it's affected by `User.current_scope`, and it's
difficult to specifically control what does or doesn't get added. If we
were starting from scratch, I don't think I'd have `joins` be affected
by `default_scope` either, but that's too big of a breaking change to
make at this point.

With this change, we no longer apply `current_scope` when bringing in
joins, with the singular exception of the motivating use case which
introduced this bug, which is providing a way to *opt-out* of having the
default scope apply to joins.

Fixes #29338.

Make the order of Hash#reverse_merge! consistent with HashWithIndifferentAccess

`arel_engine` is only used in `raise_record_not_found_exception!` to use
`engine.connection` (and `connection.visitor`) in `arel.where_sql`.

https://github.com/rails/arel/blob/v8.0.0/lib/arel/select_manager.rb#L183

But `klass.connection` will work as expected even if not using
`arel_engine` (described by `test_connection`). So `arel_engine` is no
longer needed.

Enable `Layout/FirstParameterIndentation` cop

Set `RAILS_ENV` before load application file

We have some indentation cops. But now there is a little inconsistent
params indentations. Enable `Layout/FirstParameterIndentation` cop to
prevent newly inconsistent indentation added and auto-correct to
existing violations.

Since #29725, load application file when `dbconsole` command is executed.
However, if do not set `RAILS_ENV` before reading the application file,
can not connect to the env specified in option, so added the setting
of `RAILS_ENV`.

Use frozen string literal in activemodel/

Remove unused requires

Set `represent_boolean_as_integer` via `configuration`

Fix `create_with` with multiparameter attributes

Don't cache `scope_for_create`

Allow to pass a connection to the `dbconsole` command

[ci skip]

Replace Erubis with Erubi in a part of guide [ci skip]

Running the `console` and `dbconsole` commands with a regular argument
as the environment's name automatically expand it to match an existing
environment (e.g. dev for development).

This feature wasn't available using the `--environment` (a.k.a `-e`)
option.

People should rather rely on the `-e` or `--environment` options to
specify in which environment they want to work. This will allow us
to specify the connection to pick as a regular argument in the future.

Since 0a4f6009, it's possible to specify a 3-level database
configuration to gather connections by environment.

The `dbconsole` command will try to look for a database configuration
which points to the current environment but with such flavour, the
environment key is flushed out so let's add the ability to specify
the connection and pick `primary` by default to be consistent with
Active Record.

I investigated where `scope_for_create` is reused in tests with the
following code:

```diff
--- a/activerecord/lib/active_record/relation.rb
+++ b/activerecord/lib/active_record/relation.rb
@@ -590,6 +590,10 @@ def where_values_hash(relation_table_name = table_name)
     end

     def scope_for_create
+      if defined?(@scope_for_create) && @scope_for_create
+        puts caller
+        puts "defined"
+      end
       @scope_for_create ||= where_values_hash.merge!(create_with_value.stringify_keys)
     end
```

It was hit only `test_scope_for_create_is_cached`. This means that
`scope_for_create` will not be reused in normal use cases. So we can
remove caching `scope_for_create` to respect changing `where_clause` and
`create_with_value`.

Remove unused `@last`, `@order_clause`, and `@join_dependency`

Fix `create_with` using both string and symbol

Using `@last` and `@order_clause` was removed at 8bb52746 and 90d1524a.
`@join_dependency` was added at b9599502 but it is unused in the first
place.

This is related with #27680.

Since `where_values_hash` keys constructed by `where` are string, so we
need `stringify_keys` to `create_with_value` before merging it.

Because Arel is a private API and to describe `where_values_hash` keys
constructed by `where` are string.

Do not generate unused components contents in `app:update` task

Remove blank lines in setup