Motivation
At the moment email's caption and body are hardcoded. This makes impossible to change them without changing the code.
Expected result:
The possibility to change the email's body and caption in metadata/settings should be provided.
Addition Info:
You'd need to define both under some key in i18n/en.json and qqq.json, then here use
wfMessage('key')->inLanguage('en')->text();
Since we don't want these messages translated, follow https://www.mediawiki.org/wiki/Localisation#Messages_that_should_not_be_translated