Specify properties on Microsoft.CognitiveServices/accounts apiProperties

Hey,

it seems as if for the above mentioned resource some properties are not specified as needed. If you want to create an account you need to specify an `apiProperties` sub-object within the properties but there's no documentation on that. Here it only says it has to be a not null object.

If you pass an empty object then you get this:
```
Error: Error creating Cognitive Services Account "qnamaker-stable" (Resource Group "qnamaker-stable"): cognitiveservices
.AccountsClient#Create: Failure responding to request: StatusCode=400 -- Original Error: autorest/azure: Service returne
d an error. Status=400 Code="ApiPropertiesInvalid" Message="The given 'apiProperties' '{}' is invalid. Validation errors
: Required properties are missing from object: qnaRuntimeEndpoint. Path ''."
```

So currently it's not possible to create an account with the current state of documentation so the properties should be specified in detail.

Start with the Microsoft.CognitiveServices/accounts API definition and inspect the schema for the properties.apiProperties object. Confirm which required fields the service expects, including qnaRuntimeEndpoint, then update the specification so the documented properties match successful account creation.

Written by the indexing model from the issue text.