(core) Include altSessionId in logs

Summary: Adds altSessionId to log output.

Test Plan: Tested manually.

Reviewers: paulfitz

Reviewed By: paulfitz

Differential Revision: https://phab.getgrist.com/D3355

app/server/lib/FlexServer.ts

@@ -581,6 +581,7 @@ export class FlexServer implements GristServer {
         org: mreq.org,
         email: mreq.user && mreq.user.loginEmail,
         userId: mreq.userId,
+        altSessionId: mreq.altSessionId,
       });
       return resp.status(200).send();
     }));