[C#] Simplify Enums exercise

[ErikSchierboom]

The Enums Concept Exercise requires parsing a string into a user-defined enum. The idiomatic way to do that is through Enum.Parse, which makes the generics a prerequisites. As enums are a very core data type, we feel that the generics prerequisite is a bit harsh, and that should be moved to the Advanced Enums Concept Exercise.

One benefit of this, is that enums can be used in other “simpler” exercise, without having the generics prerequisite. Another benefit would be that we can introduce the switch statement in the Enums Concept Exercise, as it is perfect for use together with enums.

In summary, the following changes should be made:

• The parsing requirement should be dropped from the Enums exercise, which means that generics won't be a prerequisite anymore.
• The Enums exercise should be redesigned to also lead the student towards using a switch in the implementation (note that a reference to the switch statement should be added to the introduction.md document).
• The Enums Advanced exercise should be redesigned to require parsing an enum. It should thus also add the generics` Concept as prerequisites.

[batibot323]

I'm all for this!

[iabdelkareem]

I can pick this one as my first contribution ^^

[ErikSchierboom]

@iabdelkareem I'm sorry, but this issue has already been assigned to @batibot323 (hence its status status/in-progress. You can look for open issues here: https://github.com/exercism/v3/issues?q=is%3Aissue+is%3Aopen+label%3Atrack%2Fcsharp+label%3Astatus%2Fhelp-wanted

[iabdelkareem]

@ErikSchierboom my bad sorry didn't notice that ^^

[ErikSchierboom]

@iabdelkareem No problem! It's fantastic that you want to help. We'll be opening lots of new issues that you can help with over the next couple of weeks.