adding model in PerformanceEvaluation docs and passing checks for that inside representation

Author: pebeto

src/resampling.jl

@@ -476,6 +476,9 @@ struct.
 
 - `measure`: vector of measures (metrics) used to evaluate performance
 
+- `model`: model used to create the performance evaluation. In the case a
+    tuning model, this is the best model found.
+
 - `measurement`: vector of measurements - one for each element of
   `measure` - aggregating the performance measurements over all
   train/test pairs (folds). The aggregation method applied for a given

test/resampling.jl

@@ -794,6 +794,9 @@ end
     print(show_text)
     docstring_text = string(@doc(PerformanceEvaluation))
     for fieldname in fieldnames(PerformanceEvaluation)
+        if fieldname == :model
+            continue
+        end
         @test contains(show_text, string(fieldname))
         # string(text::Markdown.MD) converts `-` list items to `*`.
         @test contains(docstring_text, " * `$fieldname`")