Update the mails worker to only be responsible for building the final
email using the base (layout) template and the user, team, project, and
redirect variables.
It is the responsibility of the controller to perform localization and
determine whether a custom or default email template should be used.
If the default one is used, it has to be rendered using the hello,
footer, thanks, and signature variables so that it matches the custom
template. Then, it can be sent to the worker.
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