Alignments with OpenID Federation Draft 41

[m-basili]

For 0.9.0 milestone we need to align with OpenID Federation Draft 41.

[peppelinux]

the current section about the trust infrastructure doesn't seem to have misalignments with the latest federation drafts, since we do not have redefined nothing in the italian specs but only provided an high level arch

further alignment was achieved in the following pr:
#508

[m-basili]

Some references of particular sections of the specification would need to be updated as paragraphs have been reorganized.

From the comparison with draft 36 I noticed that the client_registration_types metadata of an openid_relying_party, it is not present even if mandatory. Should we provide it?