If `collation` is given without `charset`, it may generate invalid SQL.
For example `create_database(:matt_aimonetti, collation: "utf8mb4_bin")`:

```
> CREATE DATABASE `matt_aimonetti` DEFAULT CHARACTER SET `utf8` COLLATE `utf8mb4_bin`;
ERROR 1253 (42000): COLLATION 'utf8mb4_bin' is not valid for CHARACTER SET 'utf8'
```

In MySQL, charset is used to find the default collation. If `collation`
is given explicitly, it is not necessary to give extra charset.

Allow unscoping of left_outer_joins

Change test case name to FormatValidationTest

I believe that this was caused by a copy/paste mistake.

Because `Relation` already have Arel `table`.

This is a complete fix to #30995.

Originally alias tracker will only track table aliases on
`Arel::Nodes::Join`, other args are ignored.

Since c5ab6e51, parent aliases hash will be passed then it caused the
regression #30995.

It is enough to pass list of `Arel::Nodes::Join` simply, not need to
pass garbage args which will be ignored.

Fix comment about initializers to adapt to the fact

Use SHA-1 for non-sensitive digests by default

Fix doc typo [ci-skip]

Fix some broken links in guides

Closes #31273 but we will still want to upgrade this to the
nonce-approach when it’s ready.

Fix typos, update documentation

[ci skip]

This will avoid the branch being deleted by mistake making all builds to
fail.

PostgreSQL: Allow pg-1.0 gem to be used with ActiveRecord

Fix typos [ci skip]

add instrumentation for read_multi

Add support for Minitest 5.11

When deleting through records, take into account association conditions

This option was moved into active_record_deprecated_finders in ac4d101a.

Queue_classic currently limits pg to "< 0.20".
It is therefore not used for rails CI tests. There has been
a bull request for a while (by a co-worker of mine), which
fixes the incompatibilities and extends dependencies to pg-1.x.

This patch add this pull request to the Gemfile as an interim
solution, until it is merged.

pg-1.0.0 is just released and most Gemfiles don't restrict
it's version. But the version is checked when connecting to
the database, which leads to the following error:

Gem::LoadError: can't activate pg (~> 0.18), already activated pg-1.0.0

See also this pg issue:
https://bitbucket.org/ged/ruby-pg/issues/270/pg-100-x64-mingw32-rails-server-not-start

Preparation for pg-1.0 was done in commit f28a3310,
but the pg version constraint was not yet relaxed.

`find_with_associations` is meaningless name in this point since it just
contain `construct_join_dependency` and `apply_join_dependency`, does
not contain finding anything.
If `apply_join_dependency` returns `relation` and `join_dependency` then
`find_with_associations` is no longer needed.

`relation.exists?` just wants to know if there is a result or not, does
not need the exact records matched. Therefore, an intermediate SELECT
query for eager loading is not necessary.

Fix :inverse_of documentation

[ci skip] setting :inverse_of works with :as, :through and :polymorphic options, and is needed for bi-directionality with a scope

[ci skip] Remove :conditions opion from association basics guide

This got replaced by scopes.

Need reloading when through record has replaced.

Clean up railties tests