Feature/changelog with categories

[tiwalter]

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[f-porter]

I have seen that you implemented a lot of "Mapper" and "ResponseModel" classes to control the way how data is serialized to and deserialized from JSON. Though these are not introduced with this PR I find it vital to address this issue now as these classes are resulting in a lot of maintenance effort.

To control the serialization of an object one usually uses so called custom converters that are registered in the serializer/deserializer settings or passed as list during serialization/deserialization.
This way you have to describe how to process a specific type only once and if you need to change it you can do these in one place.

In our case we want for example control how a DateTime object is serialized. For this purpose we implement a custom converter DateTimeConverter:

public class DateTimeJsonConverter : JsonConverter<DateTime>
{
    public override void WriteJson(JsonWriter writer, DateTime value, JsonSerializer serializer)
    {
        // implementation goes here
    }
    public override DateTime ReadJson(JsonReader reader, Type objectType, DateTime existingValue, bool hasExistingValue, JsonSerializer serializer)
    {
        // implementation goes here
    }
}

To use this converter for every object that is returned by the ReleaseArtifactController we have to register it. This is done in the method ConfigureServices(IServiceCollection services) of class Startup. As you are using the Newtonsoft Json package instead of the new System.Text.Json which is the new default library for ASP.NET Core 3 you have to explicitly add it, too:

services
    .AddControllers()
    .AddNewtonsoftJson(options =>
    {
        options.SerializerSettings.Converters.Add(new DateTimeJsonConverter());
    });

This custom converter is now used for every serialization and deserialization by the ASP.NET Core MVC framework (for deserializing action parameters and serializing action responses).

For deserializing an object from a file like in the method ParseDeploymentMetaInfo() of DeploymentMetaInfoMapper you either need to pass the converter as parameter to the method JsonConvert.DeserializeObject() or pass JsonSerializerSettings that contain this converter. I would prefer the latter one as this enables you to centrally define these JsonSerializerSettings, reuse them and reduce the effort to adapt these settings.