(core) switch to newer download endpoint in client

Summary:
 * Fix old download endpoint to correctly pass org info in redirect.
 * Switch to use newer download endpoint in client.

Old endpoint not removed. I started doing that, but it is used in copying, and it struck me that I'm not sure what should happen when copying from a site document to "Personal" - should it be the Personal that is associated with docs.getgrist.com currently, of should it be the Personal that is associated with the email of the user on whatever-site-we-are-on.getgrist.com. So leaving that as separate work.

Test Plan: updated tests

Reviewers: dsagal

Reviewed By: dsagal

Differential Revision: https://phab.getgrist.com/D2639

app/client/ui/ShareMenu.ts

@@ -194,7 +194,10 @@ function menuExports(doc: Document, pageModel: DocPageModel) {
     (isElectron ?
       menuItem(() => gristDoc.app.comm.showItemInFolder(doc.name),
         'Show in folder', testId('tb-share-option')) :
-      menuItemLink({ href: gristDoc.getDownloadLink(), target: '_blank', download: ''},
+        menuItemLink({
+          href: pageModel.appModel.api.getDocAPI(doc.id).getDownloadUrl(),
+          target: '_blank', download: ''
+        },
         menuIcon('Download'), 'Download', testId('tb-share-option'))
     ),
     menuItemLink({ href: gristDoc.getCsvLink(), target: '_blank', download: ''},