Update to Duende.IdentityModel

[twenzel]

• Migrate to Duende.IdentityModel
• Update Framework version
• Update some packages
  Fixes Update to Duende.IdentityModel #15

[josephdecock]

Thanks for this PR! There's a few changes to the dependencies that I want to make. While I would generally like to take the latest version of packages, especially when writing application code, our experience has been that taking a lower version is usually better, because in a nuget package, the dependency that we take establishes the minimum version, and anyone can go higher than that. That means that every time we update a dependency, that makes our requirements more restrictive, and sometimes there are weird incompatibilities (notably with System.IdentityModel) and by putting the fewest constraints in place as possible, we generally see fewer problems. I'm also going to rebase this onto main, as there have been some updates to the CI pipeline that are required to build in the last couple days.

[josephdecock]

I'm going to close this PR and open a new one, rebased onto main, just because we need the latest from main to build. Thanks very much for the PR!