Do not overwrite selected and disabled attributes

Fix release task

Add a parentheses.
related: b4c96490

Fix polymorphic preloads on NOT NULL _type columns

We have `connection_adapters/column.rb` so it's easier to remember
that the column in in a separate file.

Tiny doc fix for Strong Parameters

- accepts_nested_attribute_for -> accepts_nested_attributes_for

The new method relies on AR::Associations::Association knowing about both reflection and a model class.

AR::Base#association now raises a descriptive error when trying to access non-existent associations. Previously it would blow up with a confusing NoMethodError: undefined method `association_class' for nil:NilClass.

remove calls to sql_type on pg columns

Defer to Association#klass instead of having a custom/duplicate code.

Require yaml explicitly on #database_configuration

fixes #10613

It is already called inside type_to_sql method.

Refactor test to use DdlHelper.

Follow-Up to https://github.com/rails/rails/pull/14400

This ensures that all tables are removed after each test and thereby
allowing us to run the tests in a random order.

append link to bad code when error type is SyntaxError

Fix tests not unsubscribing from Notifications.

Ensure we are returning either `true` or `false` for `#==`

460eb83d cused `ActiveRecord::Base#==` to sometimes return `nil` in some cases,
this ensures we always return a boolean value. Also fixed a similar problem in
AR reflections.

See https://github.com/rails/rails/blob/master/activesupport/lib/active_support/notifications.rb#L131

Replace trivial regexp with string or include, twice as fast

HashWithIndifferentAccess#update respects #to_hash

Don't load test env by default.

Closes #13241

In particular, `.new`, `#update`, `#merge`, `#replace` all accept
objects which respond to `#to_hash`, even if those objects are not
Hashes directly.

Fix warning for overshadowing XML variable

Pass a base relation to build_default_scope when joining

Swap Timestamp/Callbacks order in ActiveRecord::Base