We were assigning variants in a controller, in the context of a request.
However, when sending emails, there is no request and no controller is
involved, so we also need to set the variant in the ApplicationMailer
class.
Right now this is configured using the `secrets.yml` file, which is the
file we've used in the past to configure SMTP settings.
Note that, in the `current_secrets` method, the `if default?` condition
is there so in single-tenant applications it returns the exact same
object as `Rails.application.secrets`, and it makes it immediately clear
for developers reading the code. We're also caching the tenant secrets
(using `||=`) so they behave the same way as Rails secrets; for this to
work properly 100% of the time (for example, in tests) we need to expire
these cached secrets whenever the Rails secrets change.
A similar `unless Tenant.default?` condition is present in the
ApplicationMailer because there's a chance some CONSUL installations
might not be using secrets to define the SMTP settings(they might be
using environment variables, for example) and so in this case we don't
want to force settings based on the secrets.yml file because it would
break the application.
The structure of the SMTP settings in the secrets file should be:
```
production:
tenants:
name_of_the_tenant_subdomain:
smtp_settings:
address:
(...)
```
We forgot to do so in commit d827768c0. In order to avoid the same
mistake in the future, we're extracting a method to get these
attributes. We're also adding tests, since we didn't have any tests to
check that the `dir` attribute was properly set.
We had some of the logic in the ApplicationMailer. Since we're going to
use this logic in more places, we're moving it to the Tenant model,
which is the model handling everything related to hosts.
We were duplicating the asset host and the URL host in all environments,
but we can make it so the asset host uses the URL host unless we
specifically set it.
Note that, inside the `ApplicationMailer`, the `root_url` method already
uses `default_url_options` to generate the URL.
In the rare case of CONSUL installations who have changed the asset
host, this change has no effect since they'll get a conflict in the
environment files when upgrading and they'll choose to use their own
asset host.
We're reading the value from the database, but the
`ApplicationMailer.default` method is evaluated when the application is
started. So if we don't use a Proc, we'll need to restart the server
every time we change the value in the database, or else the old value
will still be used.
Using a Proc makes sure the mailer from address is evaluated at runtime,
so emails are sent using the from address currently defined in the
database.
The same situation took place using the devise mailer. Now we don't need
to check for the settings table being present because the Proc in the
devise initializer won't be evaluated before the settings table is
created and populated.
