Calendar by ressource

Calendars are not done to be defined for each resource, like you would do on MS-Project.
Calendars just define open days (or more precisely defin off days) for categories of resources.
For instance, you can have full time resources (with just national off days), or 80% for resources not working on wednesdays...

All other "off" days for a given resource, such as holidays, sickness, or any off reason are managed using Administrative projects.
Resource then just efines real work in the future for intance to book planned holidays.