Add support for NEXA (NEXA)

[blackmennewstyle]

Commit a88b84d officially adds support for NEXA (NEXA) 🔥 🚀

In order to work properly the following procedure details how to setup a NEXA node for pool mining.

How to configure nexa config file?

(TESTNET)

# String to be appended to nexa.conf:
# rpcauth=<pool_address>:<token>
# Your password:
# <super_duper_password>
rpcauth=<pool_address>:<token>
mining.comment=<pool_address>
uacomment=<pool_address>
zmqpubhashblock=tcp://127.0.0.1:7226
net.maxConnections=25
pid=nexa.pid
par=1
rpcthreads=1
listen=1
server=1
daemon=1
rpcbind=127.0.0.1
rpcallowip=192.168.1.0/24
rpcport=7229
port=7230
debug=1

Replace respectively:
<pool_address>:<token>, see the NEXA gitlab repository in order to know how to generate the rpcauth
<pool_address> with a valid NEXA address owned by the wallet.dat

(MAINNET)

# String to be appended to nexa.conf:
# rpcauth=<pool_address>:<token>
# Your password:
# <super_duper_password>
rpcauth=<pool_address>:<token>
mining.comment=<pool_address>
uacomment=<pool_address>
zmqpubhashblock=tcp://127.0.0.1:7226
net.maxConnections=25
pid=nexa.pid
par=1
rpcthreads=1
listen=1
server=1
daemon=1
rpcbind=127.0.0.1
rpcallowip=192.168.0.0/24
rpcport=7227
port=7228
debug=0

Replace respectively:
<pool_address>:<token>, see the NEXA gitlab repository in order to know how to generate the rpcauth
<pool_address> with a valid NEXA address owned by the wallet.dat

How to configure confg.json for NEXA?

A pool configuration for NEXA be found inside the examples folder: https://github.com/blackmennewstyle/miningcore/blob/dev/examples/nexa_pool.json

Replace all the specific options with the correct expected values.
ZmqBlockNotifySocket must be the same as zmqpubhashblock= in the nexa config file.

WARNING: NEXAPOW requires very specific packages in order to be compiled properly. Be mindful to install them all, based on the build-distro-version.sh script matching your server environment. Good luck.