Part of a larger refactoring to remove type casting behavior from Arel

Part of the larger refactoring to remove type casting from Arel. We can
inform it that we already have the right type by wrapping the value in
an `Arel::Nodes::Quoted`. This commit can be reverted when we have
removed type casting from Arel in Rail 5.1

Part of the larger refactoring to remove type casting from Arel. We can
inform it that we already have the right type by wrapping the value in
an `Arel::Nodes::Quoted`. This commit can be reverted when we have
removed type casting from Arel in Rail 5.1

Part of the larger refactoring to remove type casting from Arel.

Part of the larger refactoring to remove type casting from Arel. We can
inform it that we already have the right type by wrapping the value in
an `Arel::Nodes::Quoted`. This commit can be reverted when we have
removed type casting from Arel in Rail 5.1

Part of the larger refactoring to remove type casting from Arel. We can
inform it that we already have the right type by wrapping the value in
an `Arel::Nodes::Quoted`. This commit can be reverted when we have
removed type casting from Arel in Rail 5.1

There are several valid cases where right now we can't determine the
association's class in a call to `where`. In these cases, we can fall
back to casting by looking up the column from the connection adapter
(which is what happens right now when we fall through to Arel)

This is ugly, and since we're trying to separate the concept of a type
from a column, I'd like to remove it in the future. The problem
basically comes down to this:

    Liquid.joins(molecules: :electrons)
      .where("molecules.name" => "something", "electrons.name" => "something")

The hash in this case will turn into:

    {
      molecules: { name: "something" },
      electrons: { name: "something" },
    }

What we actually need is:

    {
      molecules: {
        name: "something",
        electrons: { name: "something" },
      }
    }

/cc @mrgilman

This code could use some much heavier refactoring. It looks like
`build_relation` duplicates most of the logic of `Relation#where` and
`PredicateBuilder` with regards to handling associations and attribute
aliases

Part of the larger refactoring to remove type casting from Arel. Since
we've already cast the value a few lines above, we don't need to re-cast
it later. We can inform Arel of this by wrapping it in an
`Arel::Nodes::Quoted`, which will no longer be required in Rails 5.1

We will always have the correct type for this query, so no casting is
needed. We inform Arel that we already have the right type by wrapping
it in an `Arel::Nodes::Quoted` (which we will no longer need to do in
Rails 5.1)

This will allow eager type casting to take place as needed. There
doesn't seem to be any particular reason that the `in` statement was
forced for single values, and the commit message where it was introduced
gives no context.

See
https://github.com/rails/rails/commit/d90b4e2615e8048fdeffc6dffe3246704adee01f

Part of a larger refactoring to remove type casting from Arel.

/cc @mrgilman

[Sean Griffin & Melanie Gilman]

A custom object is required for this, as you cannot build a range
object out of `Arel::Nodes::Quoted` objects. Depends on the changes
introduced in
https://github.com/rails/arel/commit/cf03bd45e39def057a2f63e42a3391b7d750dece

/cc @mrgilman

As part of the larger refactoring to remove type casting from Arel, we
need to do the casting of values eagerly. The predicate builder is the
closest place that knows about the Active Record class, and can
therefore have the type information.

/cc @mrgilman

[Sean Griffin & Melanie Gilman]

This class cares far too much about the internals of other parts of
Active Record. This is an attempt to break out a meaningful object which
represents the needs of the predicate builder. I'm not fully satisfied
with the name, but the general concept is an object which represents a
table, the associations to/from that table, and the types associated
with it. Many of these exist at the `ActiveRecord::Base` class level,
not as properties of the table itself, hence the need for another
object. Currently it provides these by holding a reference to the class,
but that will likely change in the future. This allows the predicate
builder to remain wholy concerned with building predicates.

/cc @mrgilman

I'm attempting to remove `klass` as a dependency of the predicate
builder, in favor of an object that better represents what we're using
it for. The only part of this which doesn't fit nicely into that picture
is the check for an association being polymorphic. Since I'm not yet
sure what that is going to look like, I've moved this logic into another
class in an attempt to separate things that will change from things that
won't.

This reduces the number of places which will need to care about single
value or range specific logic as we introduce type casting. The array
handler is only responsible for producing `in` statements.

/cc @mrgilman

[Sean Griffin & Melanie Gilman]

This will allow us to pass the predicate builder into the constructor of
these handlers. The procs had to be changed to objects, because the
`PredicateBuilder` needs to be marshalable. If we ever decide to make
`register_handler` part of the public API, we should come up with a
better solution which allows procs.

/cc @mrgilman

[Sean Griffin & Melanie Gilman]

We're accidentally documenting `PredicateBuilder` and `ArrayHandler`
since there's a constant which is missing `# :nodoc:`

Construction of relations can be a hotspot, we don't want to create one
of these in the constructor. This also allows us to do more expensive
things in the predicate builder's constructor, since it's created once
per AR::Base subclass

We don't memoize the relation instance

I think we should deprecate this behavior and just error if you tell us
to do a case insensitive comparison for types which are not case
sensitive. Partially reverts 35592307

Fixes #18195

With rails/coffee-rails#61 (and #17241), the `.coffee` extension is
favoured over `.js.coffee`. Respectively, with rails/sass-rails#271
`.scss` and `.sass` are favoured over `.css.scss` and `.css.sass`.

Let's update the documentation to reflect that.

[ci skip]

Dump the default `nil` for PostgreSQL UUID primary key.

Fixed warning `possible reference to past scope` from railties

Fixed AR warning on ruby 2.2

Targeting 2.2

Remove unnecessary double space

Remove ActionController::ModelNaming

Check for Rails.env instead of Rails