This method will let you create a new guest session.
Guest sessions are a type of session that will let a user rate movies and TV shows
but not require them to have a TMDb user account.
More information about user authentication can be found
here.
You can use this method to create a fully valid session ID once a user
has validated the request token.
More information about how this works can be found
here.
Use this method to create a v3 session ID if you already have a valid v4 access token.
The v4 token needs to be authenticated by the user.
Your standard "read token" will not validate to create a session ID.