ActiveModel::Errors#merge! allows ActiveModel::Errors to append errors from
a separate ActiveModel::Errors instance onto their own.

Example:

    person = Person.new
    person.errors.add(:name, :blank)

    errors = ActiveModel::Errors.new(Person.new)
    errors.add(:name, :invalid)

    person.errors.merge!(errors)
    puts person.errors.messages
    # => { name: ["can't be blank", "is invalid"] }

Fix extracting MariaDB version

Currently `version` method always returns `5.5.5` because the
`full_version` is `5.5.5-10.x.y-MariaDB...` since MariaDB 10.x.
It should be ignored if the prefix is `5.5.5-`.

Allow mounting same engine under several locations

Fix `ActiveModel::Type::DateTime#serialize`

Mention Time.zone.parse possibly throwing ArgumentError

`ActiveModel::Type::DateTime#serialize` should return a `Time` object
so that finding by a datetime column works correctly.

Fix Parameters configuration integration tests

Now that the parameters configurations are only loaded when
ActionController::Base is we need to foce them to load in our tests. In
an application this is not needed since every request already load the
controllers.

Fix warning: `*' interpreted as argument prefix

```
/Users/kamipo/src/github.com/rails/rails/activesupport/test/core_ext/module_test.rb:402: warning: `*' interpreted as argument prefix
/Users/kamipo/src/github.com/rails/rails/activesupport/test/core_ext/module_test.rb:420: warning: `*' interpreted as argument prefix
```

Return prefixed method names from `Module.delegate`, if using prefixes

These tests relied on `ActionController::Parameters` being configured as
part of the boot process; since that now happens lazily we need to force
`ActionController::Base` to load so that we can test the behaviour.

The new tests added here ensure that `ActionController::Parameters` can
be configured from an initializer, which was broken until recently.

Fix association with scope including joins

Add missing `attr_name.to_s` in `AttributeMutationTracker`

We need to configure it only when ActionController::Base is loaded
otherwise configs on initializers will not work.

Closes #29527.

Fix `test_copying_migrations_preserving_magic_comments`

Allow the use of Bundler 2.0

Deprecate database specific JSON types

We already have database agnostic `Type::Json` since #29220.

Add missing http status codes [ci skip]

Ref: https://github.com/rack/rack/commit/5401f776f660b1f8d0e0650ba78478d7488eff75,
https://github.com/rack/rack/commit/73e08279d4433ca66cf22157a40dba562629031a

`attributes` (`values` in `LazyAttributeHash` in `AttributeSet`) has
string keys, not symbols.

Fixes #29665.

Fixes #28324.

These are no longer used since b98668de.

Using require_relative in the Rails codebase

Remove redundant `assert_respond_to`

It is covered by following assertion.

Don't wrap parameters if query parameter exists

Fix removed version 5.2 to 6.0 in the deprecation message