Should we have a setup_activation method that saves to database?

Just raising this pull request as a discussion to see if we should be adding this behaviour, or leaving it to the individual to implement on their own.

The reason is that when I saw that there was a `setup_activation` method, I assumed that it also wrote to the database -- but this turned out not to be true.

I added the following instance method:

```ruby
def setup_activation!
  setup_activation
  sorcery_adapter.save(:validate => false, :raise_on_failure => true)
end
```

Then I realised I could just have easily did the following in my own project:

```ruby
user.setup_activation
user.save
```

Which should we prefer?