Hi Guix,

I avoided doing this when fixing up GDM because it seemed a little
ham-fisted (clumsy).  However, I think it is better than all the ink
that would be spilled on help-guix without it.

In short, the point is to make sure that D-Bus services included in a
user’s profile can be found and started by the session bus.  This means
that if you are using GDM and install “evolution-data-server” and
“gnome-calendar” (for example), the session bus will be able to start
all of the services that GNOME Calendar needs to function correctly.
There are a handful of major GNOME applications that need this.

Furthermore, I think we should add “evolution-data-server” as a
propagated input for packages that require it.  This way, things like
“guix install evolution” will just work the way one expects.

Is it okay to assume that “.guix-profile” is the user’s profile like
this?  If it isn’t okay in general, is it okay enough for now?