As reported via #26904, there is a regression in how values for
Postgres' HStore column type are being processed, beginning in Rails 5.
Currently, the way that Active Record checks whether or not values need
to be serialized and put into the correct storage format is whether or
not it is a `Hash` object. Since `ActionController::Parameters` no
longer inherits from `Hash` in Rails 5, this conditional now returns
false. To remedy this, we are now checking to see whether the `value`
parameters being passed in responds to a certain method, and then
calling the `serialize` method, except this time with a real Hash
object. Keeping things DRY!