Add default structured error mapper

[Kaliumhexacyanoferrat]

As a developer of a web service application, I would like my errors to be rendered as a structured message instead of HTML, so that I can handle it more cleanly in my clients.

Example

var errorHandling = ErrorHandler.Structured();
    
var api = Layout.Create()
                .AddService<...>()
                .Add(errorHandling);

Acceptance criteria

• The functionality is implemented in the error handling module
• The functionality accepts a Serialization instance to control supported formats
• The handler renders public exception properties into the data structure
• The project templates are extended to use this error handler
• The feature is documented on the GenHTTP website
• The feature is covered by acceptance tests