Cleaner API Code with ResultFilter and ValueTuple

Examples of:

• mapping two objects into one with AutoMapper
• using a custom reusable ResultFilter to map those objects instead of writing the code in each action that requires it
• using the new ValueTuple (C#7) to pass the two objects to the filter

There's a lot of comments in the code so it should be easy to understand. If needed, additional explanation is available here: https://www.kevindockx.com/cleaner-api-code-with-resultfilter-and-valuetuple/