Multilingual Emails

[tylerjmchugh]

Is your feature request related to a problem? Please describe.
Emails are sent in the UI language of the sender regardless of the preferences of the receiver.

Describe the solution you'd like
A configuration field in settings>feedback to specify which languages to send emails in.
Email messages for all specified languages will be concatenated with a separator.
Another configuration field to specify the "translation follows" label at the start of the email. (Can include multiple languages).
If these fields are left empty, default back to the UI language.

Additional context

Working on a PR

[josegar74]

The proposal looks good. Maybe to check if can be used typeahead to select the languages, similar to what is used in #7849

It can be good to consider to add a preferred language to the user profile. So that way emails and the user interface, by default use the configuration of the user. But this is not really required.