[Feature Request] Add more APIs to identify the current user and perform actions

[akshayarora-wework]

Hey.

Couldn't find and methods to get the currently assigned user. Also had a few more doubts.

Here goes:

1.) Need a method, something like getUser.

static StatsigUser? getUser()

2.) the updateUser method will override the current user if I am trying to only append user properties, without having to re pass the user ID?
Ideally it should append user properties to the existing user.

3.) Need a method called isUserAssigned or something like that. Though this can be solved if getUser method is available.

Do let me know if there are any doubts.

Cheers!