Used MaybeCompatible for AttributeDictionary constructor threshold

The `AttributeDictionary` constructor (#99) adds some overhead to mapping operations if there aren't enough mapped attributes. To mitigate this, a threshold was previously established of five or more attributes or convertible properties (2e157e5). This was meant to account for the fact that we expect upwards of five compatible properties on the base `TopicViewModel`. With the introduction of the new `MaybeCompatible` property (6662e18, 359eaae, 1e2dc53), however, we can use a more intelligent threshold by only evaluating non-compatible properties.

In practice, some compatible properties will _still_ get mapped by the `AttributeDictionary` handling and, thus, potentially benefit from this (e.g., `View`, `IsHidden`). Mapping those will be comparatively fast, however, since they're compatible properties, so measuring off of the incompatible members remains a useful heuristic.

Author: JeremyCaney

OnTopic/Mapping/TopicMappingService.cs

@@ -196,12 +196,13 @@ public TopicMappingService(ITopicRepository topicRepository, ITypeLookupService
       if (parameters.Count is 1 && parameters[0].Type == typeof(AttributeDictionary)) {
 
         // This strategy is only performant if there are quite a several scalar properties and they are well-covered by the
-        // attributes. As a fast heuristic to evaluate this, we expect five or more attributes and properties. In practice, this
-        // should be benefitial with any more than mapped attributes, but we also expect that most topics will have 2-3 excluded
-        // or unmapped attributes (e.g., Title, LastModified) and that models will have five or properties that aren't mapped to
-        // attributes (e.g., Id, Key, WebPath). This doesn't guarantee that the attributes map to the properties, but a more
-        // accurate evaluation undermines the performance benefits of this optimization.
-        if (topic.Attributes.Count >= 5 && properties.Count(p => p.IsConvertible) >= 5) {
+        // attributes. As a fast heuristic to evaluate this, we expect five or more attributes and three or more compatible
+        // properties. In practice, this should be benefitial with any more than mapped attributes, but we also expect that most
+        // topics will have 2-3 excluded or unmapped attributes (e.g., Title, LastModified). With models, we can be a bit more
+        // intelligent, by excluding any members that are likely compatible with Topic properties, thus exluding e.g., Id, Key,
+        // WebPath, etc. This doesn't guarantee that the attributes map to the properties, but a more accurate evaluation would
+        // undermine the performance benefits of this optimization.
+        if (topic.Attributes.Count >= 5 && properties.Count(p => !p.MaybeCompatible) >= 3) {
           var attributes        = topic.Attributes.AsAttributeDictionary(true);
           arguments[0]          = attributes;
           attributeArguments    = attributes;