HttpSink does not send a valid cdevent and has no testing.

[adamkenihan]

The HttpSink option does not send an event that is valid and able to be extracted by the knative broker. I currently have a local build that sends a valid event so I can open a PR, although it lacks tests also.

[wuhuizuo]

The error happened when I send it to my webhook endpoint:

A JSONObject text must begin with '{' at 0 [character 1 line 1]