Document :combine_options

Use heredoc with credentials template

* Use heredoc with credentials template.
* Fix indentation for aws config

Fix marshaling of models with `has_many :through` associations

Fix `test_counter_cache_with_touch_and_lock_version` failure

Turns out this is still undocumented functionality.

Fix grammar bug in security guide [ci skip]

[ci skip]

Without this require, an error occurs when executing only `duration_test.rb`.
Ref: https://travis-ci.org/rails/rails/jobs/338817558#L2205-L2210

Fixes #31917

Fix `blob.service_url` for supports string type `:filename` option

- Make sure `blob.service_url` present a `ActiveStorage::Filename` type to `serivce.url`.
- Add `ActiveStorage::Filename.wrap` method.

before:

```rb
blob.service_url(filename: ActiveStorage::Filename.new("new.txt"))

blob.service_url(filename: "new.txt")
=> NoMethodError: undefined method `parameters' for "new.txt":String

params = {}
blob.service_url(filename: params[:filename])
=> NoMethodError: undefined method `parameters' for nil:NilClass
```

after:

```rb
blob.service_url(filename: "new.txt")
blob.service_url(filename: nil)
```

https://travis-ci.org/rails/rails/jobs/338338927#L1043

Related to daf15f58

Fix yaml deserialization of ActiveSupport::Duration

This ensures the duration's @parts hash has a default value, to avoid this regression introduced in 5.1:

  YAML.load(YAML.dump(10.minutes)) + 1  # => NoMethodError: undefined method `+' for nil:NilClass

In order to use `minitest_bisect` with Minitest 5.11.x, it needs to be
updated.
Ref: https://github.com/seattlerb/minitest-server/issues/2

This reverts commit 487a1061.

This `#--` is necessary for the doc of `distinct`.

[ci skip]

Update em-socksify to the latest version

Refer to a stable release of SDoc

Avoid warning: parentheses after method name is interpreted as an argument list, not a decomposed argument

Include source code in published activestorage npm package

This allows activestorage users to ship smaller javascript bundles to
visitors using modern browsers, as demonstrated in this repository:
https://github.com/rmacklin/activestorage-es2015-build-example

In that example, the bundle shrinks by 5K (24%).

In addition to allowing smaller bundles for those who ship untranspiled
code to modern browsers, including the source code in the published
package can be useful in other ways:

1. Users can import individual modules rather than the whole library
2. As a result of (1), users can also monkey patch parts of
   activestorage by importing the relevant module, modifying the
   exported object, and then importing the rest of activestorage (which
   would then use the patched object).

Note:
In order to allow the source code to be depended on rather than the
compiled code, we have to declare the external dependency on spark-md5
as a regular dependency, not a development dependency.

This means that even users who depend on the compiled code will have to
download this package. However, spark-md5 is a small package, so this
tradeoff seems worth it.

Example of multiple configurations for system test in guide [ci skip]

Currently `_default_attributes` doesn't work unless `load_schema` is
called before.

The `MissingAttributeError` is caused by `reload_schema_from_cache` is
invoked by `serialize`.

I added `load_schema` in `_default_attributes` to `_default_attributes`
works without any dependency like `attribute_types` etc.

Closes #31905.

Followup to b988ecb9, when I cherry-picked from my parallel testing
branch I didn't realize `drop` wasn't part of the commit.

You could use the `VERBOSE` env var to turn off output for migrations
tasks but you couldn't use it for other tasks.

This change moves the `verbose?` check to a method so we can also use it
in create and drop respectively.

tenderlove and I noticed this as part of the ongoing work in parallel
testing. When the parallel tests boot the app needs to create new
databases for each worker. The output from these is unnecessary but
there was previously no way to turn it off. Now if `VERBOSE=false` is
passes to `bin/rails db:create` the text "Created blah blah db" will no
longer be output.

Use `serialize_entry` throughout and introduce `serialize_entries`.

Closes #31886
Fixes #31884

Since #29572, test runner will be loaded as minitest's plugin.
Therefore, if specify a value in `Minitest.extensions` before the Minitest
initialization process, the extension will not load and the test runner will
not work.
https://github.com/seattlerb/minitest/blob/44eee51ed9716c789c7cea8a90c131cf736b8915/lib/minitest.rb#L86

Also, load processing of adapter is done before minitest option processing,
so set the adapter in the file so that the `-a` option works.

Prefer `@connection.abandon_results!` than `@connection.next_result while @connection.more_results?`

These are internally used only.

[ci skip]

Correct capitalization of "Rails" in guide text

[ci skip]

correction to #31755 as per https://github.com/rails/rails/pull/31755#discussion_r165819798