Throttling for B2B calls to notifications-push

[tosan88]

As per the discussion in #14 there would be a need to throttle for B2B accessing /content/notifications-push without affecting Next. From the comments:

tamas-molnar 
This change removes throttling for B2B clients hitting the notifications-push endpoint - taking into consideration that they don't hit Mashery beforehand (which would throttle them), is this a good idea?
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tosan88
Right, but the solution what we implemented due to Mashery's limitation of not supporting long polling makes it difficult to throttle such requests.
Do you (or somebody else) have something in mind how could we throttle B2B without affecting Next? Or should we wait for Tyk to fix it?
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lucas42
It doesn't look like Tyk is going to solve this any time soon.
Now that we have API keys being sent, is there a way to throttle the number of open connections based on those?
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tosan88
Do you have some concrete idea? I only can think of hacking what Mashery would do and I would rather not introduce something that would be the responsibility of the API Gateway