Ability to require permission for send-on-login

[RealTriassic]

A new toggle could be added under send-on-login in the configuration called require-permission just like in AuthMeVelocity Last Server Addon. The permission node could be authmevelocity.send-on-login or whatever else you decide on.

This would be useful for servers that require players to complete a test before being sent away from the login server.

[4drian3d]

Specifically for that I implemented the PreSendOnLogin event, so that some external plugin can define the necessary conditions for AuthMeVelocity to send the player to the initial server https://javadoc.io/doc/io.github.4drian3d/authmevelocity-api-velocity/latest/io.github._4drian3d.authmevelocity.api.velocity/io/github/_4drian3d/authmevelocity/api/velocity/event/PreSendOnLoginEvent.html.