Test Case - Change method name

Silence deprecation warning in test

Missed a case that only occured for mysql/mysql2

Added partial days support to `DateTime`'s `advance` method.

Call get_routes_as_head only on HEAD requests.

Railties need to be used without having to require any dependecy first.

Correctly alias table names when joining more than once

Deprecate decimal columns being automatically treated as integers

Fix redefine a has_and_belongs_to_many inside inherited class

remove unwanted `to_sym` call.

With ActiveRecord::Properties, we now have a reasonable path for users
to continue to keep this behavior if they want it. This is an edge case
that has added a lot of complexity to the code base.

Replace double quotes with single quotes while adding an entry into Gemfile

Remove `require 'active_support'` from individual modules

After ad7b5efb, which changed how
has_an_belongs_to_many used to work, we start raising an error when
redefining the same has_an_belongs_to_many association. This commits fix
that regression.

[Fixes #14983]

Let users require `active_support` before loading any ActiveSupport modules
http://guides.rubyonrails.org/active_support_core_extensions.html

All preload tests are in the eager_test file

Skip if the association was already loaded.

Remove unnecessary branch from quoting in Mysql

Add a public API to allow users to specify column types

This is already the behavior for `BigDecimal` in the abstract adapter.

See also:
https://github.com/rails/rails/commit/3a297f8db75b172882bb3c2f9440d0c7365b8b11#commitcomment-6451708

As a result of all of the refactoring that's been done, it's now
possible for us to define a public API to allow users to specify
behavior. This is an initial implementation so that I can work off of it
in smaller pieces for additional features/refactorings.

The current behavior will continue to stay the same, though I'd like to
refactor towards the automatic schema detection being built off of this
API, and add the ability to opt out of automatic schema detection.

Use cases:

- We can deprecate a lot of the edge cases around types, now that there
  is an alternate path for users who wish to maintain the same behavior.
- I intend to refactor serialized columns to be built on top of this
  API.
- Gem and library maintainers are able to interact with `ActiveRecord`
  at a slightly lower level in a more stable way.
- Interesting ability to reverse the work flow of adding to the schema.
  Model can become the single source of truth for the structure. We can
  compare that to what the database says the schema is, diff them, and
  generate a migration.

Allow empty arrays in where predicates

Extract types which don't require additional typecasting to a method

Database specific adapters shouldn't need to override `type_cast` to
define types which are already in an acceptable state.

[ci skip] Add benchmark your code section to contributing to ruby on rails guide.

I have seen many times that maintainers want people to use this gem to give
a benchmark report. It would be nice to add it and refer to it later.

Refactor reflections

Now the internal reflections will hold a reference to its public
representation, so when the outside world calls `Account.reflection` we
can build a list of public reflections.

Refactor the handling of arrays in where predicates

Simplifies the code slightly, isolates non-nil non-range values into a
single array, which will make it easier to do things like apply type
casting to them in the future.

Docs: Rename Posts to Articles in Guides' Getting Started App