[Feature request] allow a custom port

[openoms]

Would like to be able to connect a Tor-only home node running BTCPayServer to a public website through the the RaspiBlitz IP2Tor service. The service provides HTTPS communication and certificate, but it works over a custom port.

Rationale is that the subscriber to the service only rents a port on the server which translates it's HTTPS-inside-Tor traffic to clearnet HTTPS.

Currently the woocommerce plugin does not allow specifying a custom port for the connected domain.

Opening an ssh tunnel to a VPS to host the HTTPS endpoint is an alternative, but it is significantly more expensive and requires more manual steps form the user.

Related issue: https://github.com/btcpayserver/woocommerce-plugin/issues/36