feat(builder): 2-step building a facet

Author: riezebosch

src/Facet.Extensions/FacetExtensions.cs

@@ -27,6 +27,17 @@ public static TTarget ToFacet<TSource, TTarget>(this TSource source)
         return FacetCache<TSource, TTarget>.Mapper(source);
     }
 
+    public class Builder<TSource>(TSource source)
+    {
+        public TTarget To<TTarget>() where TTarget : class => source.ToFacet<TSource, TTarget>();
+    }
+    
+    public static Builder<TSource> Facet<TSource>(this TSource source)
+    {
+        if (source is null) throw new ArgumentNullException(nameof(source));
+        return new Builder<TSource>(source);
+    }
+
     /// <summary>
     /// Maps an <see cref="IEnumerable{TSource}"/> to an <see cref="IEnumerable{TTarget}"/>
     /// via the generated constructor of the facet type.

test/Facet.TestConsole/Program.cs

@@ -409,7 +409,7 @@ static void TestBasicDtoMapping(List<User> users)
 
         foreach (var user in users)
         {
-            var userDto = user.ToFacet<User, UserDto>();
+            var userDto = user.Facet().To<UserDto>();
             Console.WriteLine($"User: {userDto.FirstName} {userDto.LastName} ({userDto.Email})");
             Console.WriteLine($"  Active: {userDto.IsActive}, DOB: {userDto.DateOfBirth:yyyy-MM-dd}");
             Console.WriteLine($"  Last Login: {userDto.LastLoginAt?.ToString("yyyy-MM-dd HH:mm") ?? "Never"}");