Move everything to initializers, and replace the email settings
interceptor by a BalancerDeliveryMethod.
It has the advantage that it can be configured entirely from the
`config/environment.rb` file, without an extra file to look at.
Previously `SENDINBLUE_BALANCING` was used only when
`SENDINBLUE_ENABLED` was *disabled* (otherwise only SendInBlue was ever
used).
This commit:
- Ensure that `SENDINBLUE_BALANCING` is used only when SendInBlue is
*enabled* (which is more intuitive).
- Make it easier to add other delivery methods.
client_key is exposed to the client via gon, so if we use it for sending email too we are exposing a key so anybody could send an email.
The current client_key has a different level of right and can't send emails so it's ok to expose it.
We are making these changes in order to always use DS_Proxy. Before this change DS_Proxy was not used to write files when ActiveStorage was used directly and not through “direct upload”.
When sending emails, the mailer doesn't have access to the request
host. It needs to infer it by itself.
For this we need two settings:
- action_mailer.default_url_options, to generate urls to routes
- action_mailer.asset_host, to generate full urls to assets
Only the first one of these settings was set in production.
Fix#2518
