Feature request

Feature description
With vanilla join messages for players, normally it will just say "<player> joined the game". However, if the player who is joining previously went by another username (that the server is aware of), the vanilla join message will instead say "<player> (formerly known as <old user>) joined the game". It will only do this the first time they rejoin after having changed their username, and only that one time.

Basically, I want essentials' custom join messages to be able to display the player's old username in the same circumstances- only on the first time they rejoin. Perhaps this can be done by using a tag like {oldusername} or something, and it will only display the "(formerly known as <oldname>)" in place of the tag if the player has rejoined with a new name.

How the feature is useful
It will give server owners more options when it comes to setting up custom join messages. It'd make both server staff and players more informed about who a person is if they change their name. Right now, we need to do /seen to be able to know what their username previously was, but if it showed the old username when they logged in then that might not be necessary every single time.