add ability to mark a header or parameter value as private
We have additional credentials that are configured to be passed as additional headers. It would be nice to be able to mark these as "private" in the configuration so in the "try it" page the values that are typed in are handled like the subscription key and they appear as dots when typed. Right now when we're doing a screen share demonstration, people watching the demonstration have full view of the username and password being entered. Sure, we can go through special means to have dummy accounts or dummy systems, or change the credentials as soon as the demo is over, but they're all either cumbersome or sloppy and the preferred route would be have an option to make a given header appear and behave like the subscription key header value box on the try-it page.