Shared files - double file download

[howkymike]

Bug description

MNT-20685 commit made by @antoniojfelix introduced a bug, where a file is downloaded two times ( firstly to JS, secondly to client).
It creates 2x bigger server load and a client have to wait 2x longer. It is especially visible on the bigger files.

Proposed fix

As a fix, in the Pdfjs.js file in the downloadIfLoggedIn() function I propose to check if url contanis the "alfresco-noauth" and for the logged in validation, "/touch" API can be used.
Sample code:

downloadIfLoggedIn : function PdfJs_downloadIfLoggedIn(url)
{
      // check if site is shared
      // if yes, always download, no matter of the login state
      if(url.includes("/alfresco-noauth/"))
      {
      window.open(url, "_blank");
      return;
      }
      var request = new XMLHttpRequest();
      request.onreadystatechange = function() {
          if (this.status === 401)
          {
              // user is logged out, reload should move to login page
              window.location.reload();
          }
          else if (this.readyState == 4 && this.status == 200) {
              window.open(url, "_blank");
          }
      };
      
      // check if user has been logged out
      request.open("GET", Alfresco.constants.PROXY_URI + "touch", true);
      request.send();
}

Using the code above, there might be a problem with a 301 redirect and CORS protection (i.e. when using external auth).

Affected versions

Alfresco 7.2. and onwards.