Apply suggestions from code review

Author: baywet

src/Microsoft.OpenApi/Models/OpenApiOAuthFlow.cs

@@ -108,7 +108,7 @@ private void SerializeInternal(IOpenApiWriter writer, OpenApiSpecVersion version
             // For OpenAPI 3.1 and 3.0, serialize as an extension with x-oai- prefix
             if (DeviceAuthorizationUrl != null)
             {
-                if (version == OpenApiSpecVersion.OpenApi3_2)
+                if (version >= OpenApiSpecVersion.OpenApi3_2)
                 {
                     writer.WriteProperty(OpenApiConstants.DeviceAuthorizationUrl, DeviceAuthorizationUrl.ToString());
                 }

test/Microsoft.OpenApi.Tests/Models/OpenApiOAuthFlowTests.cs

@@ -156,9 +156,7 @@ public async Task SerializeOAuthFlowWithDeviceAuthorizationUrlAsV32JsonWorks()
             var actual = await OAuthFlowWithDeviceAuthorizationUrl.SerializeAsJsonAsync(OpenApiSpecVersion.OpenApi3_2);
 
             // Assert
-            actual = actual.MakeLineBreaksEnvironmentNeutral();
-            expected = expected.MakeLineBreaksEnvironmentNeutral();
-            Assert.Equal(expected, actual);
+            JsonNode.DeepEquals(JsonNode.Parse(actual), JsonNode.Parse(expected)));
         }
 
         [Fact]
@@ -183,9 +181,7 @@ public async Task SerializeOAuthFlowWithDeviceAuthorizationUrlAsV31JsonWorks()
             var actual = await OAuthFlowWithDeviceAuthorizationUrl.SerializeAsJsonAsync(OpenApiSpecVersion.OpenApi3_1);
 
             // Assert
-            actual = actual.MakeLineBreaksEnvironmentNeutral();
-            expected = expected.MakeLineBreaksEnvironmentNeutral();
-            Assert.Equal(expected, actual);
+            JsonNode.DeepEquals(JsonNode.Parse(actual), JsonNode.Parse(expected)));
         }
 
         [Fact]
@@ -210,9 +206,7 @@ public async Task SerializeOAuthFlowWithDeviceAuthorizationUrlAsV3JsonWorks()
             var actual = await OAuthFlowWithDeviceAuthorizationUrl.SerializeAsJsonAsync(OpenApiSpecVersion.OpenApi3_0);
 
             // Assert
-            actual = actual.MakeLineBreaksEnvironmentNeutral();
-            expected = expected.MakeLineBreaksEnvironmentNeutral();
-            Assert.Equal(expected, actual);
+            JsonNode.DeepEquals(JsonNode.Parse(actual), JsonNode.Parse(expected)));
         }
     }
 }