Fix GROUP BY aggregation alias to not duplicate "_" chars

Fix typo in autoloading constants guide  [ci skip]

Allow passing a block to the create_inbound_email_from_mail and
receive_inbound_email_from_mail test helper methods.

When you wanted to test a multipart email -- for example, an email that
has both a plaintext part and an HTML part -- there wasn't a way to
easily build one without a pre-made fixture. By allowing you to pass a
block to these methods, we unlock the power of Mail.new to easily
create a variety of emails, from multi-part emails, to emails with
attachments, and beyond.

 [ci skip]

c9e4c848 has one performance optimization for `aggregate_alias` to early
returning by `aggregate_alias.match?(/\A\w+\z/)`, but it is caused a
regression that failing deduplication for non word chars #36867.

I've quited the optimization and add a test to prevent a future
regression.

Fixes #36867.

Sync test DB from schema using its SHA1

Update azure-storage gem to latest version

Fix thread safety of prevent_writes

Previously, we used the migration status to determine whether the test
database(s) needed to be reloaded from the schema. This worked in most
cases, but if a schema.rb was modified outside of migrations or if a
migration was rolled back, it would require a manual db:test:prepare.

This commit updates load_schema to record the SHA1 of the loaded schema
file inside of the ar_internal_metadata table. We can then use this SHA
to determine whether we should reload the schema.

This ensures that the test DB stays exactly in sync with the schema
file, including rollbacks which fixes a test marked TODO.

Fix Gemfile.lock

The PR #36860 changed ActionView's required version of
rails-html-sanitizer, but I missed that we needed to run bundle,
otherwise we end up with changes every time.

Add at option to perform_enqueued_jobs test helper

As demonstrated in the test added and in #36830 the code that prevents
writes wasn't thread safe. If one thread does a read, then another does
a write, and then another does a read the second read will cause the
first write to be unwriteable.

This change removes the instance variable and instead uses a
getter/setter on Thread.current[:prevent_writes] for the connection
handler to set whether writes are allowed.

Fixes #36830

Currently, the `perform_enqueued_jobs` helpers will also immediately
perform jobs that are scheduled via `set(wait:)` to run in the future.
This commit adds a new argument to `perform_enqueued_jobs` to make it
only run jobs scheduled at or before the passed in `Time`. This allows
testing the side effects of immediate job execution separate of jobs
delayed in the future.

[ci skip] Mention `context` option of save in documentation

`ActiveRecord::Validations#save` takes `context` option
which can change validation context.
This fact should be mentioned in the documentation.

Update rails-html-sanitizer to 1.1.0 in actionview.gemspec

Commit https://github.com/rails/rails/commit/52f0b050e25cac6d9571d71c9f74ea583d8aa2b0 replaces `white_list_sanitizer` with `safe_list_sanitizer`. This is a breaking change unless the installed version of `rails-html-sanitizer` is `>= 1.1.0`.

This commit updates the minimum version in `actionview/actionview.gemspec` to `1.1.0`.

Added multiple database Active Record guide entry to the release notes

Corrected config option path in release notes for deprecation release notes of Rails 6 [ci skip]

Corrected deperecation config option path for active_record.sqlite3.represent_boolean_as_integer option in release notes. [ci skip]

Fix cookie modification during rotation

- The sanitizer has been changed to safe_list_sanitizer.
- deprecate white_list_sanitizer

Added the ability to initialize `thread_mattr_*` methods with default
values like so:

``` ruby
  class MyClass
    thread_attr_reader :foo, default: :foo
    thread_attr_writer :bar, default: :bar
    thread_attr_accessor: baz do
      "baz"
    end
  end
```

This is consistent with the api exposed by `mattr_accessor`.

Fix `PG::ConnectionBad` error when running fixtures

Use media_type instead of content_type internally

These calls to `content_type` were triggering the deprecation from
c631e8d0 in upgraded applications.

We can use `media_type` in all of these cases to avoid the deprecation.

Didn't like the complicated stuff that happened on credentials:edit. It
would append to .gitattributes multiple times. Though I see why it was
written that way.

I'm cutting off for now, but since this new flow would require each developer
to run --enable perhaps this should really be:

1. Developer enrolls Rails app by running `credentials:diff --enable`
2. credentials:edit checks .gitattributes for `diff=rails_credentials` and
   if the current file is covered by that.
3. If so, set up the "rails_credentials" driver automatically.

Helpers is more for sharing between commands. Since `Diffing` is only
for credentials we should just keep it only for credentials.

Replaces "pretty" with diffing since the former is ambiguous, while
diffing captures what it does. `opt_in` seemed clunky so it's swapped
for the one-word enable.

Address `DEPRECATED: Use assert_nil if expecting nil`