Add back checks about can user export CSV/TSV.

Thanks to marc1006 and xet7 !

Related #3173

models/export.js

@@ -80,19 +80,21 @@ if (Meteor.isServer) {
       });
     }
     const exporter = new Exporter(boardId);
-    //if (exporter.canExport(user)) {
-    body = params.query.delimiter
-      ? exporter.buildCsv(params.query.delimiter)
-      : exporter.buildCsv();
-    //'Content-Length': body.length,
-    res.writeHead(200, {
-      'Content-Type': params.query.delimiter ? 'text/csv' : 'text/tsv',
-    });
-    res.write(body);
-    res.end();
-    //} else {
-    //  res.writeHead(403);
-    //  res.end('Permission Error');
-    //}
+    if (exporter.canExport(user)) {
+      body = params.query.delimiter
+        ? exporter.buildCsv(params.query.delimiter)
+        : exporter.buildCsv();
+      res.writeHead(200, {
+        // Checking length does not work https://github.com/wekan/wekan/issues/3173
+        // so not using it here
+        //'Content-Length': body.length,
+        'Content-Type': params.query.delimiter ? 'text/csv' : 'text/tsv',
+      });
+      res.write(body);
+      res.end();
+    } else {
+      res.writeHead(403);
+      res.end('Permission Error');
+    }
   });
 }