Code review remediations

[krokicki]

I am addressing the following suggestions from the code review:

1. Michael: what does the comment on line 127 mean? - removed confusing code/comment and moved logic to separate function that can be reused
2. Anirudh: the embedded_model function is too long and not very cohesive - moved async queuing logic to a separate function, focusing the endpoint on HTTP concerns
3. Stuart: the session dict should get cleaned up or it will leak memory over time - added clean up step to stop memory leak
4. Mark: the session id should not be a UUID, it would be less convoluted and more efficient to use an integer counter - after some discussion, I decided to use a uuid4 instead of the uuid1. Since it is random it is more resistant to attacks and also makes it easier to identify different clients at a glance.