Enable extending even if scope returns nil

Remove unused `Association#interpolate`

Bring back delayed_job to test list

`delayed_job_active_record` 4.1.2 supports Rails 5.1.
Ref: https://github.com/collectiveidea/delayed_job_active_record/pull/138

If users added an attribute or otherwise changed a CurrentAttributes subclass
they'd see exceptions on the next page load.

Because `ActiveSupport::CurrentAttributes.current_instances` would keep
references to the old instances from the previous request.

We can fix this by clearing out the `current_attributes` before we unload
constants. Then any change to the model can be autoloaded again since its
slot isn't taken by an old instance.

We'll still have to call reset before we clear so external collaborators,
like Time.zone, won't linger with their current value throughout other code.

The app is booted by then, so there's no need to stash the code away in
some other script.

Since we're generating a key through the class name we can combine
the two Thread.current calls into a single hash version.

Add lazy loading to #keys and #values methods in Session

Fix regression in Numericality validator

Includes namespace in system test skelton when namespace is specified

Fixes #29247

Using `Association#interpolate` was removed since #11251.

a user input for a decimal column were ignored by numerically validations

`find` raises when it can't find a record, so we'll never reach the
else. Switch to `find_by` which returns nil when no record can be
found.

[ci skip]fix wrong variable name in docs

[ci skip]fix wrong variable name in docs

https://github.com/guard/rb-inotify/pull/49 has been merged.

Doc updates for ActiveRecord::Batches

Fix broken RDoc formatting

Update to Rails ujs readme

[ci skip]

[ci skip] Changed sentence formation for ActiveRecordRelation#update

Provides friendlier way to access queue adapters of a job.

[ci skip]

Do not show --webpack option in the plugin help message

Remove a redundant test assertion

* Add ActiveSupport::CurrentAttributes to provide a thread-isolated attributes singleton

* Need to require first

* Move stubs into test namespace.

Thus they won't conflict with other Current and Person stubs.

* End of the line for you, whitespace!

* Support super in attribute methods.

Define instance level accessors in an included module such that
`super` in an overriden accessor works, akin to Active Model.

* Spare users the manual require.

Follow the example of concerns, autoload in the top level Active Support file.

* Add bidelegation support

* Rename #expose to #set. Simpler, clearer

* Automatically reset every instance.

Skips the need for users to actively embed something that resets
their CurrentAttributes instances.

* Fix test name; add tangible name value when blank.

* Try to ensure we run after a request as well.

* Delegate all missing methods to the instance

This allows regular `delegate` to serve, so we don't need bidelegate.

* Properly test resetting after execution cycle.

Also remove the stale puts debugging.

* Update documentation to match new autoreset

CI against JRuby 9.1.10.0

fixed indentation.

rebased with master.

- removed predicate method. Used only reader.

Remove unused test class