Closes#5350
- No longer necessary to initialize via async init().
- Adds a startup-check for mail configuration.
- Creates a notification in the admin client if
mail transport is "direct" and sending a message fails.
closes#5489
- Remove unneeded Promise.promisify in mailer
- Remove noEmailTransportConfigured error as not relevant anymore (Direct is default)
- Clone message argument in mailer.send
- Move test from api_mail_spec to mail_spec
- Add default mail title test