Incorrect macro used in `test_capability`
It seems that the method
test_capability @ server/red-channel.h#L78 is used both for testing the VD_AGENT capabilities AND the auth capabilities in @ server/reds.c#L2355. This is technically incorrect and could cause issues in the future.
I suggest a new set of macros be added to protocol.h for set/clear/test specifically for the common_caps.