Indicate whether request body is required

[cmeeren]

Currently, the requestBody's required attribute is not rendered:

      requestBody:
        required: true
        content:
          application/json:
            schema:
              type: object
              properties:
                data:
                  type: string

There should be an indicator for a required request body.

Furthermore, I suggest that to avoid confusion, optional request bodies are labelled explicitly as optional (perhaps only when adding an explicit requried: false?). This is because it's easy to confuse whether the request body is required with whether the attributes of a top-level object is required. For example:

requestBody:
  required: false
  content:
    application/json:
      schema:
        type: object
        required:
          - data
        properties:
          data:
            type: string

As rendered, I would expect the API to require a request body containing an object with the data attribute. However, the API requires EITHER an empty request body OR an object with the data attribute. An explicit optional indicator at the request body level could alleviate this confusion.