Foreign Key Support

[metaskills]

Let's turn on supports_foreign_keys? and see what we need to do. As is now, there are two tests that fail since they are not wrapped in connection guards to see if foreign keys are supported. They will likely go away or need to be worked on during this feature work.

ActiveRecord::AdapterTest#test_foreign_key_violations_are_translated_to_specific_exception
ActiveRecord::AdapterTest#test_foreign_key_violations_are_translated_to_specific_exception_with_validate_false