Address ORA-00972: identifier is too long when tested with Oracle

by using shorter attribute names.

Dump PostgreSQL primary key with custom function as a default.

[ci skip] Improve documentation consistency for ActiveModel::Errors

*   Leave two blank lines between sections/packages for readibility.

*   Always indent bullet points with four spaces. This allows multi-paragraph
    points to align properly (see #16103), and it is the same as the format we
    already use in CHANGELOGs. Doing this consistently sets an easy precedent
    for future contributors to follow.

*   Always put the PR/commit link on its own line in the source. If the bullet
    point spans multiple paragraphs, put it on its own paragraph at the end.

[Godfrey Chan & Juanito Fatas]

[ci skip] Fix typos like `a html` to `an html` and 'an mail' to 'an email'.

Fix tests broken in #16149

Refactor Hash#transform_values and Hash#transform_values!

[Bug report templates] Added rack master to the Gemfile [ci skip]

Conflicts:
	activerecord/lib/active_record/base.rb

This reverts commit 0f6b101e.

Reason: It's better to let `unscope` be documented. We can add a
separate section for `except`.

Just so it's clearer what's going on in the following assertion.

/cc #11993 @robin850

Silence Downloader's output

Fixing typo in comment

Use NameError#name to assert raised error.

This output isn't used anywhere for assertions so we can simply remove
it. The introducing commit was f238d495.

Don't rely on the column SQL type for bit string quoting

Use a type object for type casting behavior on SQLite3

[Guides] Sentence break for clarity [ci-skip]

Fix incorrect unsubscription.

Use `#bytesize` instead of `#size` when checking for cookie overflow

Although the cookie values happens to be ASCII strings because they are
Base64 encoded, it is semantically incorrect to check for the number of the
characters in the cookie, when we actually want to check for the number of the
bytes it consists of.

Furthermore it is unecessary coupling with the current implementation that
uses Base64 for encoding the values.

Also reordered some of the items to put newer ones on top (same order as
CHANGELOGs), which makes it easier to diff while we are still working on it.

Removed the single space character for Safari

`render nothing: true` or rendering a `nil` body no longer add a single
space to the response body.

The old behavior was added as a workaround for a bug in an early version of
Safari, where the HTTP headers are not returned correctly if the response
body has a 0-length. This is been fixed since and the workaround is no
longer necessary.

Use `render body: ' '` if the old behavior is desired.

For example, if use pgcrypto extension in PostgreSQL 9.4 beta 1, where
uuid-ossp extension isn't available for moment of writing, and thus to
use a gen_random_uuid() method as a primary key default.

In this case schema dumper wasn't able to correctly reconstruct
create_table statement and lost primary key constraint on schema load.

Fixes #16111.

  Address CVE-2014-4671 (JSONP Flash exploit)