Updating Associations::Preloader docs

Replace drop sql statement to drop_table method

to drop sequences at the same time each tables dropped for Oracle

[ci skip]Correct variables in the sample code

Since cc03675d30b58e28f585720dad14e947a57ff5b the error message became like
"Could not load database configuration. No such file -"
which doesn't really tell what's actually missing.

[ci skip] application.rb -> development.rb in web-console docs

Removed any default margin from mail preview body.

/cc @yahonda

Closes #10247.

The same goes for tables with an "id" column but without primary key constraint.
Reading from the view works without configuration. If you have an updateable view
you need to use `self.primary_key = ''`.

SQLite3Adapter now checks for views in table_exists? fixes: 14041

Conflicts:
	activerecord/CHANGELOG.md

`AbstractAdapter#supports_views?` defaults to `false` so we have to turn it on
in adapter subclasses. Currently the flag only controls test execution.

/cc @yahonda

Remove extra newline from ActiveJob test template

[ci skip] change the line orientation on asset precompile page

Closes #16684.

This is achieved by always generating `GeneratedAssociationMethods` when
`ActiveRecord::Base` is subclassed. When some of the included modules
of `ActiveRecord::Base` were reordered this behavior was broken as
`Core#initialize_generated_modules` was no longer called. Meaning that
the module was generated on first access.

minor fix for #16846

Merge pull request #16846 from prathamesh-sonpatki/document-error-handling-in-transactions-callbacks

Update upgrading guide about error handling in transactional callbacks [ci skip]

- Part of 16576
- [ci skip]

Remove extra 'has been' from deprecation warning about asserting selectors

[ci skip]

Remove extra 'has been' from the deprecation message

- [ci skip]

Add docs for web-console to 4.2 Upgrade Guide

Memoizing will not make possible to assert the output of the view if it
is changed after the first assert_select call

Related with plataformatec/simple_form#1130 and rails/rails-dom-testing#15

disable migrations logging while running test cases for AR schema tests

Fix query with nested array in Active Record

Removing unused fake models

Cleanup SchemaDumper

* Add private method primary_key_for, which more clearly shows that the
expected return value is nil when a primary key is not found.

* Consistent whitespace
* Remove unnecessary parentheses