settings: fix for default web browser

[sergio-costas]

This fix allows to set and check the default web browser, thus removing the nasty message that Firefox isn't your default browser.
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[codecov]

Codecov Report

Merging #16 (fcba778) into master (0da6ea8) will decrease coverage by 0.04%.
The diff coverage is 25.00%.

❗ Current head fcba778 differs from pull request most recent head bc7b34e. Consider uploading reports for the commit bc7b34e to get more accurate results

@@            Coverage Diff             @@
##           master      #16      +/-   ##
==========================================
- Coverage   78.61%   78.57%   -0.04%     
==========================================
  Files         992      992              
  Lines      122905   122935      +30     
==========================================
- Hits        96620    96597      -23     
- Misses      20210    20250      +40     
- Partials     6075     6088      +13     

Flag	Coverage Δ
unittests	78.57% <25.00%> (-0.04%)	⬇️

Flags with carried forward coverage won't be shown. Click here to find out more.

Impacted Files	Coverage Δ
interfaces/builtin/desktop.go	91.42% <ø> (ø)
usersession/userd/settings.go	54.80% <25.00%> (-18.23%)	⬇️

... and 6 files with indirect coverage changes

[jhenstridge]

I think this could be simplified a bit by dropping the xdg-open and xdg-settings proxy scripts from core22-desktop and replacing them with the xdg-utils versions. I don't think there is anything in ubuntu-desktop-session that needs the proxies, and this would simplify the snapd changes here, since snap userd could just rely on the scripts in /usr/bin.

With luck, this would also fix snaps trying to use the xdg-open proxy...

[kenvandine]

gnome-control-center might call xdg-settings in the default apps panel.

[jhenstridge]

gnome-control-center might call xdg-settings in the default apps panel.

It doesn't. It uses the g_app_info_set_as_default_for_type glib API, which makes equivalent changes to $XDG_CONFIG_HOME/mimeapps.list directly.

[kenvandine]

This looks good to me now