Launchpad should return header Content-Type: text/plain;charset=UTF-8

[Tiago Stürmer Daitx]

Text files nowadays are quite likely in UTF-8 and Launchpad should default to it when setting text/plain for the "Content-Type" header - it should be set to "text/plain;charset=UTF-8"

I usually see the browser using the wrong charset for various text/plain files: changelogs, changes, diffs, attachments, etc.

For example, the 2 following .changes and a .diff files

- https://launchpadlibrarian.net/501144131/openjfx_11.0.7+0-2ubuntu2_source.changes

- https://launchpadlibrarian.net/465885965/openjdk-lts_11.0.6+10-2ubuntu1_11.0.6+10-2ubuntu2.diff.gz

are rendered incorrectly in Firefox because it defaults to 'Western'.

Using "Firefox Hamburger Menu -> More -> Text Encoding -> Unicode" fixes that and the text is rendered in the correct encoding.

Chromium is not affected and defaults to Unicode due to its own charset detection logic.

I believe that defaulting to the UTF-8 charset is more reasonable nowadays than defaulting to the Western (ie. iso-8859-1) charset.

[Tiago Stürmer Daitx (tdaitx)]

This would also fix bug 1059752 for which - at the time - would made not much sense to default to UTF-8 just yet.