Add EnumValueObject

Hey together,

before creating a pull request I wanted to retrieve some feedback for the following new type: EnumValueObject The basic idea is that have a better enumeration type in the eco-system of the CSharpFunctionalExtensions.

It has the following construct when used:

public class Language : EnumValueObject<Language>
{
   public static readonly Language German = new Language("de");

   public static readonly Language English = new Language("en");

   protected Language(string key) : base(key)
   {
   }
}

The main advantage over a “normal” enum would be:

• Type-Safety (the Create method returns a Result<TEnumValueObject>)
• Extendable without extension methods

To see the reference implementation which I would like to merge in this repository head over to my repository: EnumValueObject

[vkhorikov]

Yes, I plan to do a full-blown documentation of all features, including this one. Issue for tracking: https://github.com/vkhorikov/CSharpFunctionalExtensions/issues/255

[vkhorikov]

Great! Pushing this with v2.15.0.

Not closing the issue as a reminder to see if the code can be refactored toward inheritance.