Improve C# code sample for saving nodes

[tombasche]

I noticed this code sample in the tutorial wasn't very idiomatic C# code, and there is perhaps a more type-safe way to handle saving of nodes within a project using interfaces.

[tetrapod00]

It's worth noting that it was previously considered to use interfaces for this exact page in an earlier issue #6622 (comment):

There are plenty of examples of this in the documentation, see the Saving Games page, which uses duck typing and Godot's JSON serializer while it may better to use interfaces and one of .NET's more powerful serializers.

[tombasche]

Interestingly, from the linked issue, this was also one of my concerns when writing this PR 😅 I'm glad it isn't just me.

though I'm worried that users may be confused as to where IHittable is coming from, since it's not a type provided by Godot or the BCL, we'll likely want to add some text explaining what it is and then that may be confusing to GDScript users.

[tetrapod00]

You might be able to use the second codeblock (under https://docs.godotengine.org/en/latest/tutorials/io/saving_games.html#serializing) to also include the definition of ISaveable. Maybe use // comments to distinguish which file each line is in, which is often bad practice (separate codeblocks are better) but in this case since the text and codeblocks in these tutorials are designed for GDScript then adapted for C#, there's only so much you can do.