Rename test method

When looking for mutation, we compare the serialized version of the
value to the before_type_cast form. `Type::Serialized` was breaking this
contract by passing the already serialized attribute to the subtype's
mutation detection. This never manifested previously, as all mutable
subtypes either didn't do anything in their `serialize` method, or had a
way to detect double serialization (e.g. `is_a?(String)`). However, now
that JSON types can handle string primitives, we need to avoid double
serialization.

Fixes #24993.

Signed-off-by: NJeremy Daer <jeremydaer@gmail.com>

Define ActiveRecord::Attribute::Null#type_cast

Improve documentation and tests for raw_host_with_port and host_with_…

When calling remove_connection in a subclass, that should not fallback
to the parent, otherwise it will remove the parent connection from the
handler.

Using ActiveRecord::Base.attribute to declare an attribute with a default value on a model where the attribute is not backed by the database would raise a NotImplementedError when model.save is called.

The error originates from https://github.com/rails/rails/blob/59d252196b36f6afaafd231756d69ea21537cf5d/activerecord/lib/active_record/attribute.rb#L84.
This is called from https://github.com/rails/rails/blob/59d252196b36f6afaafd231756d69ea21537cf5d/activerecord/lib/active_record/attribute.rb#L46 on an ActiveRecord::Attribute::Null object.

This commit corrects the behavior by implementing ActiveRecord::Attribute::Null#type_cast.

With ActiveRecord::Attribute::Null#type_cast defined, ActiveRecord::Attribute::Null#value (https://github.com/rails/rails/blob/59d252196b36f6afaafd231756d69ea21537cf5d/activerecord/lib/active_record/attribute.rb#L173..L175) can be replaced with its super method (https://github.com/rails/rails/blob/59d252196b36f6afaafd231756d69ea21537cf5d/activerecord/lib/active_record/attribute.rb#L36..L40).

fixes #24979

Getting Started Guide: Add invoke test_unit to files table [ci skip]

Added clarity to documentation of ArrayInquirer#any? [ci skip]

- Added clarity to documentation of ArrayInquirer#any? [ci skip]

- Added clarity to documentation of ArrayInquirer#any? [ci skip]

Getting Started Guide: Add channels and jobs to purpose table [ci skip]

API only apps: Preserve request format for HTML requests too

Dont cache the conn_spec_name when empty

`remove_connection` can reset the `connection_specification_name`, so we
need to to set it after the remove_connection call on
`establish_connection` method.

We cannot cache the connection_specification_name when it doesnt
exist. Thats because the parent value could change, and we should keep
failling back to the parent. If we cache that in a children as an ivar,
we would not fallback anymore in the next call, so the children would
not get the new parent spec_name.

[ci skip] Update documents of `ConnectionHandler`

Getting Started Guide: Update Ruby version to 2.3.1p112 [ci skip]

[ci skip]

Follow up of #24844.
The key of `@owner_to_pool` was changed from `klass.name` to
`spec.name`. By this change "memory leaks in development mode"
will not happen, bacause the equality of string is not changed
by reloading of model files.

remove_connection

When calling `remove_connection` on a model, we delete the pool so we also
need to reset the `connection_specification_name` so it will fallback to
the parent.
This was the current behavior before rails 5, which will fallback to the
parent connection pool.

[fixes #24959]

Special thanks to @jrafanie for working with me on this fix.

- Earlier we were responding with JSON format for HTML requests in a API
  app.
- Now we will respond with HTML format for such requests in API apps.
- Also earlier we were not testing the API app's JSON requests
  properly. We were actually sending HTML requests. Now we send correct
  JSON requests. Also added more test coverage.
- Based on the discussion from this commit -
  https://github.com/rails/rails/commit/05d89410bf97d0778e78558db3c9fed275f8a614.

[Prathamesh Sonpatki, Jorge Bejar]

Minor syntax change

While working on this very example recently, I found that Rails will throw POST errors if you leave an empty block in front the `format.js` when using either `remote: true` or vanilla  JS/JQuery.

Should quote `lock_name` to pass to `get_advisory_lock`

Replacement cycle for readability

Fix Gemfile.lock by updating rails-dom-testing

- Followup of https://github.com/rails/rails/pull/24946.

Update rails-dom-testing gem to 2.0

Resolves #24924.