FIX: Lazy on key-many-to-one was using "true" instead of "proxy"

Author: jagregory

src/FluentNHibernate.Testing/DomainModel/Mapping/CompositeIdentityPartTester.cs

@@ -53,6 +53,15 @@ public void KeyManyToOneDefaults()
                     .HasAttribute("class", typeof(CompIdChild).AssemblyQualifiedName);
         }
 
+        [Test]
+        public void KeyManyToOneLazySetToProxyForTrue()
+        {
+            new MappingTester<CompIdTarget>()
+                .ForMapping(c => c.CompositeId().KeyReference(x => x.Child, m => m.Lazy()))
+                .Element("class/composite-id/key-many-to-one")
+                    .HasAttribute("lazy", "proxy");
+        }
+
         [Test]
         public void KeyManyToOneExplicitColumnName()
         {

src/FluentNHibernate.Testing/MappingModel/Output/XmlKeyManyToOneWriterTester.cs

@@ -58,7 +58,7 @@ public void ShouldWriteForeignKeyAttribute()
         public void ShouldWriteLazyAttribute()
         {
             var testHelper = new XmlWriterTestHelper<KeyManyToOneMapping>();
-            testHelper.Check(x => x.Lazy, true).MapsToAttribute("lazy");
+            testHelper.Check(x => x.Lazy, true).MapsToAttribute("lazy", "proxy");
 
             testHelper.VerifyAll(writer);
         }

src/FluentNHibernate/MappingModel/Output/XmlKeyManyToOneWriter.cs

@@ -41,7 +41,7 @@ public override void ProcessKeyManyToOne(KeyManyToOneMapping mapping)
                 element.WithAtt("foreign-key", mapping.ForeignKey);
 
             if (mapping.HasValue(x => x.Lazy))
-                element.WithAtt("lazy", mapping.Lazy);
+                element.WithAtt("lazy", mapping.Lazy ? "proxy" : "false");
 
             if (mapping.HasValue(x => x.NotFound))
                 element.WithAtt("not-found", mapping.NotFound);