CloudEventBuilder should fail when providing an invalid extension name

[slinkydeveloper]

The CloudEventBuilder should fail with the proper exception (look at CloudEventRWException#newInvalidExtensionName) if the user is trying to add an extension with a bad name (as specified here https://github.com/cloudevents/spec/blob/master/spec.md#attribute-naming-convention)

[arghya88]

@slinkydeveloper So withExtension need to be overridden like withAttribute in CloudEventBuilder to achieve this?

[slinkydeveloper]

WDYM needs to be overriden? This issue is just about changing the impl of CloudEventBuilder to check the name of the extension: https://github.com/cloudevents/sdk-java/blob/master/core/src/main/java/io/cloudevents/core/impl/BaseCloudEventBuilder.java#L99

[arghya88]

My bad...Understood now
/assign