Mark ChatCompletionResponseMessage content and `function_call.{name…

…,arguments}` as required

I'm not certain this is correct, but I don't think we've ever seen anything different. 

Doing this allows types to flow from a response into a request during a function call flow seamlessly; without this, it's quite a pain for the user.

openapi.yaml

@@ -1957,8 +1957,12 @@ components:
  arguments:
  type: string
  description: The arguments to call the function with, as generated by the model in JSON format. Note that the model does not always generate valid JSON, and may hallucinate parameters not defined by your function schema. Validate the arguments in your code before calling your function.
+ required:
+ - name
+ - arguments
  required: 
  - role
+ - content
 
  ChatCompletionStreamResponseDelta:
  type: object