Drop obsolete Devise::Models::Authenticatable#inspect method

[OutlawAndy]

Rails has handled parameter filtering for a number of years now. So this PR just follows through on the suggestion made in this comment

Fix #5274

Thank you!

[justwiebe]

This would be great, thanks!

[carlosantoniodasilva]

I think this makes sense, but I want to mention that there'll be a slight change in the behavior of #inspect because it relies on serializable_hash which uses UNSAFE_ATTRIBUTES_FOR_SERIALIZATION, and that means any of those attributes that don't match filter_parameters values will now show up in #inspect.

Either way, I agree it's something worth delegating back to Rails, mentioning it in the changelog.

Would it make sense to ensure Devise includes things like password and token in the Rails params filter automatically? (even though it's normally part of the rails new setup.)

[OutlawAndy]

@carlosantoniodasilva Do you suggest that I push Models::Authenticatable::UNSAFE_ATTRIBUTES_FOR_SERIALIZATION into config.filter_parameters in the Devise railtie? Or something else?

I'll also need to update the failing test. As you stated, this changes the behavior from removing keys to masking values.

Also, should I add an entry to the changelog or is that something you will do when a new version is released?

Thank you for the quick response and attention to this!