[Railties] Add config rake_eager_load

Update instructions in generated Postgresql database.yml.

Delegate child session assertions to parent session

Some code examples were missing the language used for code highlighting.

Add backend API doc for action text [ci skip]

Remove call to object_id

minor grammar fix

Update documentation to explain the behavior of explicitly raising ActiveRecord::Rollback in a nested transaction [skip ci]

Add some examples for getting current_user

Remove `spring-watcher-listen` from default Gemfile

Reversible remove_columns

Update The Rails Initialization Process page[ci skip]

Fix FrozenError on ActiveModel::Error clear and delete

Update downloading section

Respect Content-Type header passed in head method

Move `name` key on configuration hash into `DatabaseConfig`

Update .yardopts to document *.rb files in [GEM]/app

`name` is used by Rails to find the configuration by connection
specification name, but database adapters don't need to use `name` in
order to establish a connection. This is part of our work to separate
what the database needs to connect (the configuration hash) and the
what Rails needs to find connections (everything else).
Co-authored-by: NJohn Crepezzi <john.crepezzi@gmail.com>

Also close PRs with no activity over 3 months

Make `belongs_to_required_by_default` a class attribute:

* Add failing ActiveJob exceptions test for "disable retry jitter"

Thanks to @kaspth for the starting point.

* Update ActiveJob retry jitter to correctly use zero value

* Simplify "disable retry jitter" test

We don't need to repeat this many times. Fewer is shorter.

* Refactor determine_delay with jitter

* Fix indentation

* Close the curtains and give JITTER_DEFAULT some privacy

* Use .zero? instead of == to check jitter value

* Add ActiveJob test for explicit zero jitter
Co-authored-by: NKasper Timm Hansen <hey@kaspth.com>
Co-authored-by: NCliff Pruitt <cliff.pruitt@cliffpruitt.com>

- I'm hoping to get this change accepted even though this flag was
  introduced years ago in 6576f735

  My use case is the following:

  We were never enforcing belongs to association and we have a lot
  of models that implicitely declare an association as optional.
  We are now changing all our models to make associations required
  by default.
  Since we have a lot of models (more than 1000), I'd like to
  progressively enable them to use the `belongs_to_required_by_default`
  flag.

  The problem is that this flag is a mattr_accessor and doesn't to be
  set per model. We basically need to modify all our models (which
  could take years) before being able to modify the global flag.

  I'd like to change this flag to a class_attribute to solve the
  issue.

Deprecate `connection_config`

Rename a test method to not conflict with a deprecated method

This method in test has a confusing name that also is the same as a
method with a different behavior on `ActiveRecord::Base` so we're just
renaming it to avoid confusion between the two!
Co-authored-by: Neileencodes <eileencodes@gmail.com>

Add a host method to HashConfig

Removes the un-used function call for syntaxhighlighterConfig

The `connection_config` method returns a `Hash`, but since we're moving
toward a place where we're using `DatabaseConfiguration::DatabaseConfig`
objects everywhere, we're introducing a new method here to replace it
called `connection_db_config`.
Co-authored-by: Neileencodes <eileencodes@gmail.com>

This is the last property that's used directly inside of Rails (in
`DatabaseTasks`) that doesn't have an accessor in `HashConfig`.

Adding this so that we can have a uniform interface for accessing
properties that Rails needs (that descend from
`DatabaseConfigurations::DatabaseConfig`)
Co-authored-by: Neileencodes <eileencodes@gmail.com>

Revert revert ec sqlite3 connection transaction

Ensure migration generator respects primary key config in references

When rails is configured to use a specific primary key type:
```
config.generators do |g|
  g.orm :active_record, primary_key_type: :uuid
end
```

Previously:

    $ bin/rails g migration add_location_to_users location:references

The references line in the migration would not have `type: :uuid`.
This change causes the type to be applied appropriately.
Co-authored-by: NDermot Haughey <hderms@gmail.com>

- #37798 had to be reverted because a new flakyness appeared ([see
  CI build](https://buildkite.com/rails/rails/builds/65467#efaa1dd5-aaf4-43a1-a204-d1c42abf614d))

  This failure isn't related to the change itself.
  If you apply this diff, the test will some time to time fail.
  Even without my changes.

  ```diff
  diff --git a/activerecord/test/cases/transactions_test.rb b/activerecord/test/cases/transactions_test.rb
index b5c1cac3d9..09fe0ddd7f 100644
--- a/activerecord/test/cases/transactions_test.rb
+++ b/activerecord/test/cases/transactions_test.rb
@@ -1127,7 +1127,6 @@ def test_no_automatic_savepoint_for_inner_transaction
   end
 end if Topic.connection.supports_savepoints?

-if ActiveRecord::Base.connection.supports_transaction_isolation?
   class ConcurrentTransactionTest < TransactionTest
     # This will cause transactions to overlap and fail unless they are performed on
     # separate database connections.
@@ -1198,4 +1197,3 @@ def test_transaction_isolation__read_committed
       assert_equal original_salary, Developer.find(1).salary
     end
   end
-end
  ```

  SQlite3 isn't safe to run in a multi threaded environment unless
  sqlite is compiled with a special flag which isn't our case.
  Ref https://www.sqlite.org/threadsafe.html

number_to_currency negative zero fix

document the default for dependent activerecord option