Closes #21563.

The `name` argument of `add_references` was both used to generate the
column name `<name>_id` and as the target table for the foreign key
`name.pluralize`.

It's primary purpose is to define the column name. In cases where the
`to_table` of the foreign key is different than the column name we
should be able to specify it individually.

Move the methods for schema dumping into `{mysql,postgresql}/schema_dumper.rb`

Allow mysql and mysql2 tests run by database user with password

ActionMailer https on URL with force_ssl = true

Current master branch includes many schema dumping improvements.
It extract these features to the appropriate files.

Remove deprecated pg_dump -i flag

Move schema definiton classes into the appropriate files

Change `Journey::Route#verb` to return string instead of regexp.

* Revises the name of Rails components (they have a space).

* Uniform word wrap at column 80..

* Uniform punctuation, according to our guidelines.

* Minor edits of details seen in passing.

do not generate manifest.js in plugins

[ci skip] Fix typo in deep_dup docs

Since the plugin generator do not generate assets, I think manifest.js also that it unnecessary.

Current master branch includes many schema creation improvements in
MySQL. It extract these features to the appropriate file.

Current master branch includes many schema definition improvements in
MySQL. It extract these features to the appropriate file.

Make AR#increment! and #decrement! concurrency-safe

Allow multiple `root` routes in same scope level

When an application has multiple root entries with different
constraints, the current solution is to use `get '/'`. Example:

**Currently I have to do:**
```ruby
get '/', to: 'portfolio#show', constraints: ->(req) { Hostname.portfolio_site?(req.host) }
get '/', to: 'blog#show',      constraints: ->(req) { Hostname.blog_site?(req.host) }
root 'landing#show'
```

**But I would like to do:**
```ruby
root 'portfolio#show', constraints: ->(req) { Hostname.portfolio_site?(req.host) }
root 'blog#show',      constraints: ->(req) { Hostname.blog_site?(req.host) }
root 'landing#show'
```

Other URL matchers such as `get`, `post`, etc, already allows this, so I
think it's fair that `root` also allow it since it's just a shortcut for
a `get` internally.

Fix cache fetch instrumentation

used predicate methods to avoid is_a? checks

update to ruby-oci8 - 2.2.0

It stopped `ruby 1.8` support, we already switched to `ruby >= 2.2.2`

monitor is require for SneakersAdapter

change `prepare_destination` to public API [ci skip]

With the previous implementation, the block passed to
define_singleton_method, which will live forever as the method body,
captures the parameters (args and block) in its enclosure.

For the current_scope registry, that can include an AR::Relation.

Modify the scope method documentation

Follow DRY principle and remove duplication

Remove unused require

`require 'active_support/core_ext/string/filters'` was added in b3bfa361. However, it is no longer needed from 3ae98181.

Minor cleanup for form helpers guide

remove unused require

Fix subsecond precision supported version

Improve readability in CSRF section of guide [ci skip]

`shellwords` is no longer needed from #20605.

Remove unused `pk_and_sequence_for` in AbstractMysqlAdapter