Use ticketing system for follow and share APIs

[pct960]

This will help in keeping track of the follow requests. For e.g. when a user makes a follow request he/she is issued with a ticket number. They can poll for its status using, say, /status/<ticket_no> instead of subscribing to the notify queue. When the owner has to approve a follow request with a share they would simply use the ticket number along with the status update, say, approved or denied