It is possible, on the IP -> Hotspot menu, on the settings for the Purple WiFi Hotspot that you set up, to allow clients to bypass the Captive Portal (that is our hotspot service). It should be possible in the future to 'allow' clients based on their MAC via the Portal systems, but for not, on a Mikrotik, you might, on the Hosts tab of the Hotspot, right click on the MAC of the connected device, and select 'Make Binding'
and from there select the 'Type' of 'binding' as "bypassed"
In that way when the MAC is encountered connecting to the Hotspot it gets a connection to the internet without having to use the Hotspot login process. This would also exclude the 'client' from the stats that our systems provide.
If this needs to be permanent bypass you may find this only works so far as the IP Lease for that connection to the Hotspot, and if the IP Lease expires it may break this relation with the Hotspot binding and you will have to delete the and recreate the binding.
To prevent this from happening it's better to start by creating a static IP lease based on the MAC address of the device you're wanting to allow, so; to start with you need to go to DHCP Server & make the connection static (so go to IP -> DHCP Server -> Leases -> filter by MAC again to isolate the device in question and click on the 'Make Static' button)