feat: update doc following core API migration and 2.0.0 release (#14)

- feat: describe missing endpoints used to set / remove rights on entities
- feat: update contract for get authorized entities endpoint
- feat: global update for new architecture in 2.0.0
- feat: add migration procedure to upgrade to 2.0.0

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Co-authored-by: Gaël Poujol <76944966+gpoujol@users.noreply.github.com>
Co-authored-by: gpoujol <gael.poujol@egm.io>