VFS serves files with wrong encoding

Steps to reproduce

• Create page Sandbox.VFS.WebHome.
• Attach zip containing an HTML with file encoded in UTF-8 and containing characters with accents (see sample test.zip).
• Generate URL to that HTML file using the VFS API, for example:

$services.vfs.url("attach:Sandbox.VFS.WebHome@test.zip/index.html")

• Then visit the page at the generated URL.

Actual result

The file is served with a content-type whose charset is not always UTF8. For instance on my machine, the response content-type header shown by the browser network inspector is: "text/html;charset=iso-8859-1". As a result, the file characters are not displayed correctly.

Environment

• XS 14.4 bundled in Jetty with default flavor
• Java 11
• Environment locales:

ubazj@ubazj:~$ locale
LANG=en_US.UTF-8
LANGUAGE=
LC_CTYPE="en_US.UTF-8"
LC_NUMERIC=fr_FR.UTF-8
LC_TIME=fr_FR.UTF-8
LC_COLLATE="en_US.UTF-8"
LC_MONETARY=fr_FR.UTF-8
LC_MESSAGES="en_US.UTF-8"
LC_PAPER=fr_FR.UTF-8
LC_NAME=fr_FR.UTF-8
LC_ADDRESS=fr_FR.UTF-8
LC_TELEPHONE=fr_FR.UTF-8
LC_MEASUREMENT=fr_FR.UTF-8
LC_IDENTIFICATION=fr_FR.UTF-8
LC_ALL=