V12: Named json options

[Zeegaan]

Notes

With the switch to Swashbuckle, we had some trouble serializing plain object types, when receiving one of these types, we would convert it into a JsonElement, which is hard to work with.
This PR remedies that, instead of converting object types to JsonElement, we instead convert the objects to JsonObject.

This gave us some additional challenges, because we can't "just" add our Converters and be done with it. As that would also force anyone using Umbraco to serialize our way (or other projects, like the incoming content delivery API)
We have resolved this by adding our own AddJsonOptions extension, that now also takes a settings name.

We can then register our options like so:

  .AddJsonOptions("BackOffice", options =>
  {
      // all back-office specific JSON options go here
      options.JsonSerializerOptions.PropertyNamingPolicy = JsonNamingPolicy.CamelCase;
      options.JsonSerializerOptions.Converters.Add(new JsonStringEnumConverter());
      options.JsonSerializerOptions.Converters.Add(new JsonObjectConverter());
  });

And decorate our controller with:

[JsonOptionsName("BackOffice")]
public class ManagementApiControllerBase : Controller
{

}

• Added JsonObjectConverter class to handle the actual converting of object types.
• Added MvcBuilderExtensions which contains our extension method of AddJsonOptions()
• Added ConfigureMvcJsonOptions which handles inserting our custom input/output formatters

How to test

(Try a few different endpoints, they should work as expected)

• Modify the TelemetryViewModel class like so:

public class TelemetryViewModel
{
    [JsonConverter(typeof(JsonStringEnumConverter))]
    public TelemetryLevel TelemetryLevel { get; set; }

    public object MyObject { get; set; } = new object();
}

• Call the Get endpoint https://localhost:44331/umbraco/management/api/v1/telemetry/level
• This should not recurse forever and cause StackOverflow, but instead return the telemetrylevel and an empty object
• Set a breakpoint in the SetTelemetryController.SetConsentLevel method
• Try posting to the same endpoint with the property as a string, int, etc. and assert it gets deserialized properly

{
    "telemetryLevel": "Basic",
    "myObject": "test"
}

{
    "telemetryLevel": "Basic",
    "myObject": 123
}

[nikolajlauridsen]

Found a couple of minor things, otherwise, it looks good 👍

Tests out good as well 😄