This mod removes the max counter from villagers, allowing you to trade with them as often as you want to. Your villagers will never run out out stuff to trade, and never have to restock – as long as you have trade goods or emeralds, villagers will want to trade for them.
Also, villagers will never increase their prices due to demand (you need version 1.1 for that).
Needs to be installed on the server. Does not need to be installed on the client. The file doubles as a spigot/paper plugin, so if you put it into the plugins directory on your spigot/paper server, you’ll get infinite trades there as well.