About user_id and Get User's Profile endpoint

[DREWiex]

Hi, there!

Simple question: what are the user_id restrictions? I.e. is it case sensitive? what is the maximum length? I'm handling errors in my app and I noticed that when I make the call to the Get User's Profile endpoint and the user doesn't exist it returns status 500, but when the user is invalid it returns status 400, so it's a bit confusing.

I appreciate the help!

P.S: I apologize for my English.