[showcase][xs]: private showcase page is not visible while INPROGRESS - refs #142
[showcase][xs]: private showcase page is not visible while INPROGRESS - refs #142

* previously, when dataset is in progress, the showcase was available for any user because it loads the page using response from specstore only. Now we check "findability" property in respinse from specstore and if it is private, we check if hash of useremail matches userid returned from resolver.

datahq/frontend,datahq/frontend