[Draft] nk20 v2.0.0 with django 4.2

I start a migration to python3.11 (debian Bookworm) and django 4.2 (#123). It pass tests but:

• linters fail because of a breaking change fix, and I'm not sure how to fix it
• i'm note sure that there is no bug, so additionnal tests are needed
• documentation update is needed
• i had to remove CAS (and htcpcp-tea) which are not compatible with django 4.2. Maybe found a solution for the CAS (the only use is belenios, maybe another authentification is possible)
• OAuth secret are now hashed, check are needed before an irreversible action
• maybe there are no more used/not optimal code

Moreover, because it's an important update, I think it could be v2.0.0 of the "note kfet 2020":

• we can publish a v1.1.0 with the version before migration if someone want to use a release with django2.2
• someone has a version name idea ?
• some additional change could be made (see milestone %nk20 v2.0.0 with django 4.2 , feel free to add tickets)