Camelize Kotlin model names and filenames (#8085)

Previously the case of the names could be inconsistent if there were nested object properties. Eg. 'MyNewPet_barking_type' now becomes 'MyNewPetBarkingType'.
Ideally, we should use nested classes to take advantage of the namespace of the parent class, but this is much more work.

Author: PatrickNLT

modules/swagger-codegen/src/main/java/io/swagger/codegen/languages/AbstractKotlinCodegen.java

@@ -453,13 +453,22 @@ public String toModelName(final String name) {
         String modifiedName = name.replaceAll("\\.", "");
         modifiedName = sanitizeKotlinSpecificNames(modifiedName);
 
+        // Camelize name of nested properties
+        modifiedName = camelize(modifiedName);
+
         if (reservedWords.contains(modifiedName)) {
             modifiedName = escapeReservedWord(modifiedName);
         }
 
         return titleCase(modifiedName);
     }
 
+    @Override
+    public String toModelFilename(String name) {
+        // Should be the same as the model name
+        return toModelName(name);
+    }
+
     /**
      * Provides a strongly typed declaration for simple arrays of some type and arrays of arrays of some type.
      *

modules/swagger-codegen/src/test/java/io/swagger/codegen/kotlin/KotlinClientCodegenModelTest.java

@@ -221,9 +221,9 @@ public static Object[][] modelNames() {
         return new Object[][]{
                 {"TestNs.TestClass", new ModelNameTest("TestNs.TestClass", "TestNsTestClass")},
                 {"$", new ModelNameTest("$", "Dollar")},
-                {"for", new ModelNameTest("`for`", "`for`")},
-                {"One<Two", new ModelNameTest("One<Two", "OneLess_ThanTwo")},
-                {"this is a test", new ModelNameTest("this is a test", "This_is_a_test")}
+                {"for", new ModelNameTest("`for`", "For")},
+                {"One<Two", new ModelNameTest("One<Two", "OneLessThanTwo")},
+                {"this is a test", new ModelNameTest("this is a test", "ThisIsATest")}
         };
     }