Restore test deliveries for ActionMailer.
Add Missing Test Cases for the constantize
Merge pull request #15567 from aditya-kapoor/add-cases

Add Additional Test Cases for the constantize
Handle client disconnect during live streaming

.. even when the producer is blocked for a write.
Merge pull request #15452 from matthewd/live-abort

Handle client disconnect during live streaming
Merge pull request #15545 from zuhao/refactor_actionpack_assert_select_test

Restore test deliveries for ActionMailer.
Ignore distressingly-frequent segfaults on this build

Not sure what's causing them suddenly, but it seems unlikely there's
much we can do about it. For the small amount of coverage this
particular job gains us, it's hurting us more, by making CI failures
unremarkable.
Update migrations.md

default column type modifier
Merge pull request #15571 from kalmanh/patch-1

Update migrations.md
Mail 2.6.1 silences excessive warnings; remove Gemfile hack

Completes https://github.com/rails/rails/pull/15493

Revert "For our build, stick with mail 2.5.x for now"

This reverts commit b8f586a094c104006d29a87fee0d8b48d0af2d14.
Merge pull request #15573 from bf4/mail_2_6_1_released

Mail 2.6.1 silences excessive warnings; remove Gemfile hack
rm cached attributes

The original patch that added this concept can be found
[here](https://web.archive.org/web/20090601022739/http://dev.rubyonrails.org/ticket/9767).
The current default behavior is to cache everything except serialized
columns, unless the user specified otherwise. If anyone were to specify
otherwise, many types would actually be completely broken. Still, the
method is left in place with a deprecation warning in case anyone is
actually still calling this method.