Draft: release/v2.0.0

This MR aims to do some simplifications in order to have a simple documentation and a simpler code.

We:

• delete RPC dependancies, and go for Restfull decidim side
• delegates decidim operations to decidim Rest API
• remove strapi graphql and goes to Restfull api

This allows us to have a unified documentation, that is simple enough to understand for everyone.