Refactor resource calendar and resource mixin:
- add a required timezone field on models 'resource.calendar' and 'resource.resource';
- resource calendar attendances are now computed in the timezone of the resource
or the calendar;
- improve API of 'resource.calendar' and 'resource.mixin';
- avoid other modules from using the implementation methods of 'resource.calendar';
- refactor implementation of 'resource.calendar' to make it more efficient.
Purpose is to replace existing inherits of resource.resource by an inherit
on the mixin itself. The mixin offers several methods to compute working
intervals, attendance, hours, ... This mixin will be improved in future
commits when new methods that will be required with future improvements
of various service apps.
This commit also adds tests for the mixin itself. A new model is defined
only for testing purpose to test the mixin.
Raphael Collet