User role support

follow up of https://github.com/Open-EO/openeo-aggregator/issues/64

Now, EGI based user role handling is only done at level of aggregator (very simple permission simple: user that is not enrolled properly will not be able to do authenticated requests).

This system has to be moved to openeo-python-driver/openeo-geopyspark-driver, with some things in mind:

• generalize to not only handle the current EGI user role system from openEO platform but also other role/permission systems
• fine-grained permissions on level of collections, processes, job resources, credits, ...?

首先查看链接的后续 issue 以及 aggregator 中当前的角色处理方式。拟议的工作涉及 openeo-python-driver 和 openeo-geopyspark-driver，包括泛化基于 EGI 的角色，以及为集合、过程、作业资源和积分定义细粒度权限。要视为完成，需要在这些方面形成一致认可的设计并完成实现。