contrasti

AWS is not acceptable choice if you want to stand to your values, see e.g.:

https://gizmodo.com/amazon-is-aggressively-pursuing-big-oil-...

In france you have OVH - the invest heavily in solar energy and build datacenters with low energy consumption in mind. That might be a better choice (not working for them).

the only problem we found is the integration with our own authorization system

But integration with external authorization systems is an extremely basic requirement for every piece of software, certainly on the top 5 on the requirements list for every serious solution - I can not understand how did you forget about this?