Template encoding screwed up

When adding templates with special characters (e.g. umlauts), the template ends up being exposed with screwed up encodings.

My impression is that the template encoding in the database is UTF-8 and Django delivers it as UTF-8 as well. But apparently no encoding header is added to the HTTP response, so the HTTP client (mailman3 core and web browsers) screw up the encoding.

This leads to broken characters in mails that contain templates with umlauts.