Hotel mixin sample -- Components, slices

Components interact
and build on each other, but some can be safely removed without impairment of
the rest of the software. Here is a diagram of the dependencies:

FIXME ILLU

Hotel mixin sample -- repositories
Hotel mixin sample -- reservation mixin
Hotel mixin sample -- accommodation mixin
Hotel mixin sample -- discount mixin mixin
Hotel mixin sample -- queue mixin mixin