find_in_batches should not mutate its argument
Modify the session serializer implementation

Rename allowed options to :marshal and :json, for custom serializers
only allow the use of custom classes.
Merge pull request #13888 from rails/session-serializer

Modify the session serializer implementation
docs, `references` is only used with `includes`. Closes #13727.

There is no gain in `referencing` tables that are not used for preloading.
Furthermore it will break if polymorphic associations are invloved. This
is because `references_eager_loaded_tables?` uses all `reference_values`
to decide wether to `eager_load` or `preload`.
tidy CHANGELOGs [ci skip]
Merge pull request #13878 from marcandre/leave_my_options_alone

find_in_batches should not mutate its argument
Add `travel_back` to remove stubs from `travel` and `travel_to`
Remove automatic removal of Date/Time stubs after each test case

This behavior is only work out-of-box with minitest and also add a
downside to run after each test case, even if we don't used the travel
or travel_to methods
Improve documentation [ci skip]