This is a simple plugin to put your server into maintenance mode.
This example is written for the Minecraft version 1.19.
You may set the message to be displayed during maintenance in the config.yml.
Tells the executing player if the server is in maintenance mode or not.
Permissions: spigotmaintenance.info
Enable maintenance mode.
Permissions: spigotmaintenance.enable
Disable maintenance mode.
Permissions: spigotmaintenance.disable
Players with this permission are allowed to join the server during maintenance.