With #31615 `type_for_attribute` accepts either
a symbol as well as a string. `has_attribute?` and `attribute_alias`
also accept either. Since these methods call `to_s` on the argument,
we no longer need to do that at the call site.

This suppresses `Timeout::Error` exceptions.
Ref: https://travis-ci.org/rails/rails/jobs/334622442#L1089-L1110

This example was added in abdf546a
but was inconsistent with `composed_of :balance` definition in the
'Customer'.

[Ryuta Kamizono & bogdanvlviv]

[ci skip]

This reverts commit 755f7b58, reversing
changes made to 35db4603.

Originally `mapping: %w(balance amount)` is correct mapping example.

Closes #31346.

[Ryuta Kamizono & bogdanvlviv]

[ci skip]

Allow type_for_attribute(:symbol)

Added tests for ActiveStorage::Blob#image? and ActiveStorage::Blob#video?

Follow up of #31724.

If `composed_of` objects have multiple mappings, array predicate handler
can not correctly handle the expanded condition.

We need to handle it like polymorphic association objects.

Remove joke in security guide [ci skip]

I think this is a joke, although not a great one.
It's mildly unprofessional, so I think we
should get rid of it.

Fix not expanded problem when passing an Array object as argument to the where method using composed_of column.

Define `supports_foreign_tables?` in AbstractAdapter

Remove out-of-date references to jQuery [ci skip]

Fixes #31703

This was changed with 5d7b70f4 and 428939be.

Because we use `credentials` in an example of configuration files, but
`credentials` can not be used unless it is 1.8.0 or later.

Ref: 9d65ac30

Relax minitest versions

We locked Minitest to 5.11.1 in #31799
because 5.11.2 included a breaking change.
The change was fixed in 5.11.3, so we no
longer need to lock in the version.

Fix infinite loop when unloading autoloaded modules 

Fix example migrations in Associations guide

Use respond_to test helpers

Add failing test for infinite loop when unloading autoloaded modules when an error occured during the load.

Since #29504, mysql2 adapter lost ability to insert zero value on
primary key due to enforce `NO_AUTO_VALUE_ON_ZERO` disabled.
That is for using `DEFAULT` on auto increment column, but we can use
`NULL` instead in that case.

Lock Minitest 5.11.1

To workaround `undefined method `error?' for` reported
at https://travis-ci.org/rails/rails/jobs/333456146

Fix not expanded problem when passing an Array object as argument to the where method using composed_of column.

Fixes #31723

```
david_balance = customers(:david).balance
Customer.where(balance: [david_balance]).to_sql

# Before: WHERE `customers`.`balance` = NULL
# After : WHERE `customers`.`balance` = 50
```

Update note on MySQL index order support [ci skip]