If reuse `QUOTED_TRUE` and `QUOTED_FALSE` without frozen, causing the
following issue.

```
Loading development environment (Rails 5.1.0.alpha)
irb(main):001:0> ActiveRecord::Base.connection.quote(true) << ' foo'
=> "1 foo"
irb(main):002:0> ActiveRecord::Base.connection.quote(true) << ' foo'
=> "1 foo foo"
irb(main):003:0> type = ActiveRecord::ConnectionAdapters::AbstractMysqlAdapter::MysqlString.new
=> #<ActiveRecord::ConnectionAdapters::AbstractMysqlAdapter::MysqlString:0x007fd40c15e018 @precision=nil, @scale=nil, @limit=nil>
irb(main):004:0> type.serialize(true) << ' bar'
=> "1 foo foo bar"
irb(main):005:0> type.cast(true) << ' bar'
=> "1 foo foo bar bar"
```

Fix an exception where content-type is nil

Previously we had primarily tested the behavior of these attributes by
calling `.new`, allowing this to slip through the cracks. There were a
few ways in which they were behaving incorrectly.

The biggest issue was that attempting to read the attribute would
through a `MissingAttribute` error. We've corrected this by returning
the default value when the attribute isn't backed by a database column.
This is super special cased, but I don't see a way to avoid this
conditional. I had considered handling this higher up in
`define_default_attribute`, but we don't have the relevant information
there as users can provide new defaults for database columns as well.

Once I corrected this, I had noticed that the attributes were always
being marked as changed. This is because the behavior of
`define_default_attribute` was treating them as assigned from
`Attribute::Null`.

Finally, with our new implementation, `LazyAttributeHash` could no
longer be marshalled, as it holds onto a proc. This has been corrected
as well. I've not handled YAML in that class, as we do additional work
higher up to avoid YAML dumping it at all.

Fixes #25787
Close #25841

Where appropriate, prefer the more concise Regexp#match?,
String#include?, String#start_with?, or String#end_with?

In Ruby ^ and $ mean start and end of *line*.

A regexp that validates an email should not check if
some line of the string looks like an email, and maybe
be surrounded by the entire Joyce's Ulysses. What the
regexp has to check is if the string itself looks like
an email.

This validator is used only in tests, the ^/$ anchors
implied no risk.

Add proper description for `Rails.cache.fetch` [ci skip]

It all started noticing some foo.method({ ... }) method calls
in passing. This is a whole pass modernizing this file.

While some string literals are edited where I touched code,
this pass does not uniformizes quotes. A ton are left untouched
on purposes. We have no defined style.

Where appropriatei, prefer the more concise Regexp#match?,
String#include?, String#start_with?, or String#end_with?

Explain meaning of the code very well and Remove confusion. [ci skip]

Code like `render(topics) => render("topics/topic")` adds confusion
for the readers. On first impression, that code feels like hash kind
of data, but it's not. So make it more clear and meaningful.

Adds `not_in?` onto Object

The exclamation mark is not a metacharacter.

Where appropriate prefer the more concise Regexp#match?, String#include?,
String#start_with?, and String#end_with?

Some casual benchmarks showed a 2x factor.

All credit goes to @nurse.

See the rationale in the documentation included in this patch.

We are going to gradually introduce this predicate in the code base.

AEAD modes like `aes-256-gcm` provide both confidentiality and data authenticity, eliminating the need to use MessageVerifier to check if the encrypted data has been tampered with.
Signed-off-by: NJeremy Daer <jeremydaer@gmail.com>

Fix incorrect indentation in method comment

For consistency mainly.

Also, some have a name that could make the reader think they
enforce the opposite of what they do, because the default is
not visible there.

Enforce minimal web-console version for Rails 5

I dropped the version constraint in web-console with the idea it will be
easier to upgrade the console between Rails releases. However, issues
like #25899 started popping up.

I'm reintroducing the constraint, but this time, I don't set an upper
limit to the major version. This will keep the web-console in a version
that always works for the current Rails version and can be easily
upgraded to the last one with `bundle update`.

We may need to backport this for Rails 5.0.1.

Fixes #25899.

Bring back support for callable cache key when rendering collection

Remove tab chars before commands to be run

Fix explain logging with binds

Add `exists?` and `update_all` to `CollectionProxy` for respects an association scope

Remove Oracle specific tests based on deprecated behaviors

 - Refer https://github.com/rsim/oracle-enhanced/pull/845
Remove `set_date_columns` which has been deprecated in Oracle enhanced adapter
 - Refer https://github.com/rsim/oracle-enhanced/pull/869

`binds` is an array of a query attribute since Active Record 5.0.