Improve render plugin selection
Summary:
This now considers two additional attributes:
- the message mimetype, with the most specific matching one considered first
- a plugin priority to disambiguate as a last resort
This became necessary with the fairly aggressive syntax highlighting
plugin also triggering on vcard or ical attachments. Their plugins now
have priority, as their mimetypes are more specific than text/plain the
highlighting plugin is registered for.
Reviewers: knauss
Reviewed By: knauss
Subscribers: KDE PIM
Tags: KDE PIM
Differential Revision: https://phabricator.kde.org/D8195