support enums in convertToPropertyValue

Introduce some tests for convertToPropertyKey. I tried to add tests for
convertToPropertyValue but I am not familiar enough with DartObject in
the analyzer to get it done.

Author: nicholasphair

openapi-generator/lib/src/openapi_generator_runner.dart

@@ -328,6 +328,7 @@ class OpenapiGenerator extends GeneratorForAnnotation<annots.Openapi> {
     return value.toStringValue() ??
         value.toBoolValue()?.toString() ??
         value.toIntValue()?.toString() ??
+        value.getField('_name')?.toStringValue() ??
         '';
   }
 }

openapi-generator/pubspec.yaml

@@ -15,5 +15,6 @@ dependencies:
   openapi_generator_cli: ^4.0.0
 
 dev_dependencies:
+  test: ^1.23.1
   pedantic:
 

openapi-generator/test/test.dart

@@ -0,0 +1,28 @@
+import 'package:openapi_generator/src/openapi_generator_runner.dart';
+import 'package:test/test.dart';
+
+
+void main() {
+  group('convertToPropertyKey()', () {
+    final generator = OpenapiGenerator();
+
+    test('convert "nullSafeArrayDefault"', () {
+      expect(generator.convertToPropertyKey('nullSafeArrayDefault'),
+          equals('nullSafe-array-default'));
+    });
+
+    test('convert "pubspecDependencies"', () {
+      expect(generator.convertToPropertyKey('pubspecDependencies'),
+          equals('pubspec-dependencies'));
+    });
+
+    test('convert "pubspecDevDependencies"', () {
+      expect(generator.convertToPropertyKey('pubspecDevDependencies'),
+          equals('pubspec-dev-dependencies'));
+    });
+
+    group('convertToPropertyValue()', () {
+      // TODO.
+    });
+  });
+}