Prevent device from connecting multiple times in the same session?

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I would like to restrict my (web-based) game in a way that prevents one user from opening multiple tabs and connecting each of them to the photon server at the same time. Ideally, only one or two connections should be allowed per user/device such that one cant be seen as multiple ccu.

What would be the easiest way to do this with Photon? Thank you for any help you might give me.