Services page in UI requires http request body to be JSON

The page of the CDAP UI from which a user can make a request to user services allows a POST/PUT body.
However, there is the restriction that the text typed into the input box for the request body must be of type JSON.
However, user services can be written in a way to also expect non-JSON content type; for example, a string such as 'abc'.
It is perfectly fine to have an http request's body to be non-JSON.

Furthermore, the UI requests that the strings in the be quoted with double quotes; single quotes will not make the submit button green/clickable.