String additions to GNOME Software 3.28 for purchase errors

[Robert Ancell <robert ancell gmail com>]

Hi,

I'd like to request a string freeze break for a change in GNOME Software [1].

The change is to add new error messages when purchasing apps. This code is not currently used by any in-tree plugins so is unlikely to be seen by any current user.

The strings are:
"Unable to purchase %s: authentication was required"
"Unable to purchase %s: authentication was invalid"
"Unable to purchase %s: no payment method setup"
"Unable to purchase %s: payment was declined"
"Unable to purchase %s"

Thanks,

--Robert

[1] https://gitlab.gnome.org/GNOME/gnome-software/merge_requests/28