Hey vidhyut_cisco,
Through the API you can only subscribe yourself or make a global subscription.
One possibility I can think of is to pass a session key to the endpoint and have the endpoint use the session key in rest calls.
Otherwise, I think you will have to add the ability to subscribe as any user as an idea via rest to our Idea Board.
Hope this helps,
Yuri
To expand on what YuriK mentioned, if you're already authenticated to the REST API as a user with sufficient permission (i.e. an admin), it's actually pretty easy to get a session key for another user. See here:
This is the relevant portion:
"Log in as the specified user, and return a session key identifying the session created for the login. The authentication parameters can consist of... A login name only. This will succeed if the user associated with the call (via session key or cookies) has the permission "allow_switch_users" for the community."
So once you have the session key for the desired user, you can make the subscription call as that user.
