Blacklisting Players from using your shop

[TheFarawayDev]

Is your feature request related to a problem? Please describe.
Our server has people who will resale so we tried to blacklist but saw there was no feature to do so and in which caused our server to die off as people got frustrated because of this!

Describe the solution you'd like
The ability to stop certain players from buying from a specific shop and the ability to allow them again.

Describe alternatives you've considered
The ability to instead whitelist players to use your shops but this would be more tedious!