This test https://github.com/rails/rails/blob/master/activerecord/test/cases/base_test.rb#L381
is failing because is not setting `CreditCard.pluralize_table_name` to `false`.

In this case, i prefer to change to another model that is not in the `GUESSED_CLASSES`
array.

fix order dependent test in AggregationsTest

Ensure class variable is set to nil.

It prevents the following test to fail:

    def test_do_not_run_the_converter_when_nil_was_set
      customers(:david).non_blank_gps_location = nil
      assert_nil Customer.gps_conversion_was_run
    end

Check https://github.com/rails/rails/blob/master/activerecord/test/models/customer.rb#L7
for more information.

serialized attribute value is not from the same class

We need more ❤ in this file. There are a lot of outdated entries.

We reverted the removal because the new deprecation policy

This reverts commit 7a8aee08.

This reverts commit a7f4b0a1.

Conflicts:
	activerecord/lib/active_record/associations/has_one_association.rb
	activerecord/lib/active_record/persistence.rb
	activerecord/test/cases/base_test.rb
	activerecord/test/cases/dirty_test.rb
	activerecord/test/cases/timestamp_test.rb

Refactored common date and time calculations.

Allow to pass Symbol or Proc into :limit option of #accepts_nested_attributes_for

Instead of building a Blog::Post instance for every test in form helper
tests, just build it in the test that uses it.

correct handling of date selects when using both disabled and discard options

we should take disabled option not only from `html_options` hash but from
`options` hash too like `build_select` method does it. So

datetime_select("post", "updated_at", { :discard_minute => true }, { :disabled => true })
datetime_select("post", "updated_at", :discard_minute => true , :disabled => true)

both these variants work now

closes #7431

We simplify two things here: First since * is greedy it is enough to go
look for the rightmost ::, no need to ask the regexp engine to match the
rest of the string since we are not validating anything, only capturing.
The second simplification comes from using a look-ahead assertion, that
allows us to have the capture in $&, thus removing the need of a group.

Accept a symbol for `:in` option on inclusion and exclusion validators

Extract ActiveRecord::SessionStore from Rails

Tell people to install `activerecord-session_store` gem when it's not
installed instead ofraising `NameError` on missing
`ActionDispatch::Session::ActiveRecordStore`.

This functionality will be available from gem
`active_record-session_store` instead.

Fix tests that depend on run order

The new regexp has less work to do, we anchor a fixed string at the end
and need no group.