Chaining multiple proxy results in rejected shares
I am pretty sure it should be possible to chain multiple Stratum proxy one after the other. However, it doesn't work with this proxy. If I make my miner go through 2 of them, then every shares will be rejected by the 2nd proxy (the one closer to the pool) with the message: `Invalid nonce; is miner not compatible with NiceHash?`.

The cause is this chunk: https://github.com/xmrig/xmrig-proxy/blob/23b8d9e6fa4c9f22fd97e45cd8954d9adee6efda/src/proxy/Miner.cpp#L183-L185

If I just comment out the `reject` call, then the miner's shares are accepted and I can see them on the pool's website. So I'm not sure exactly what this test is for, but it seems to block some uses cases that seem valid.

I was just curious about what a Stratum proxy does and thought this should work. This might not be much of an issue to anyone, but it might indicate a deeper issue.