Testing non-Rails apps with modules requires factories to define fully namespaced classes

Description

FactoryBot throws an error when defining factories that refer to classes within modules in non-Rails applications. FactoryBot will work, but the class used by the factory must be explicitly stated in the full namespace. Simply updating the GETTING_STARTED.md document should be sufficient.

Reproduction Steps

# bar.rb
module Foo
  class Bar
    ...
  end
end

# factories.rb
FactoryBot.define do
   factory :bar do
    ...
  end
end

Produces this error:
NameError: uninitialized constant Bar

Working Code

# bar.rb
module Foo
  class Bar
    ...
  end
end

# factories.rb
FactoryBot.define do
   factory :bar, class: 'Foo::Bar' do
    ...
  end
end

I'm happy to update GETTING_STARTED.md to explain better and help rookies like me who might get stumped.

Read GETTING_STARTED.md and compare its factory examples with the non-Rails reproduction in the issue. Document that factories for classes inside modules should use the full namespace, such as class: 'Foo::Bar'. Done when the guide clearly explains the requirement and includes a working example.