KafeProblemDetails

See merge request !59

I really don't want to care about XML.

All unhandled exceptions now result in a 500 response with KafeProblemDetails.

Implement a custom IClientErrorFactory so that MVC action results (other than ValidationError) work properly

Effectively forbid anyone from generating MVC's ProblemDetails from controllers, since they now throw a NotSupportedException.

Configure ApiBehaviorOptions to turn ModelState errors into ObjectResults containing KafeProblemDetails

Also replace ErrorJsonConverter with a modifier function for the DefaultJsonTypeInfoResolver.

This will make it play nicer with ASP.NET Core's model binder.

We'll just create them localized instead based on Accept-Language. It doesn't make sense to send all the error messages in all language variants we support.

Added MUNI favicons

See merge request !60

Update to .NET 9

See merge request !58

Also update all NuGet packages

Project locking and auth redirects

See merge request !57