The way we set up email sending completely changes with Spree 2. This
change encapsulates that code in a single method so that it can be
changed easily and doesn't create further merge conflicts while we are
still working on the master branch and the Spree upgrade.
Using deferred methods on the user model breaks delayed jobs when the
user is deleted while the job still exists. We could create a proper job
referencing a user id for sending these emails instead. But since the
user has to wait for the confirmation email anyway, we can send it
within the current request. This should be revised if performance
becomes an issue.
Sending the email directly also has the advantage that we can tell the
user if emailing failed. See the following commits.
This change impacts a bunch of specs as we now need a working email
setup to create unconfirmed users. This commit introduces a custom
matcher to unify testing for confirmation emails.
