Function: Remove a topic from user’s subscriptions

Function: Add a forum to user’s subscriptions

Function: Add a topic to user’s subscriptions

Function: Handles the front end toggling of forum subscriptions

Function: Remove a forum from user’s subscriptions

Function: Check if a forum is in user’s subscription list or not

Function: Check if a topic is in user’s subscription list or not

Function: Get a user’s subscribed topics

Function: Get the users who have subscribed to the forum

Function: Get the users who have subscribed to the topic