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AutoAdmin for V1.0.24 e0.0.20

Add your name to the list
list={"your name", "other admin names too"}

This will chat "welcome back" to the joining admin in SP, and MP to confirm. (and DS on subsequent joins)
This will chat "Hello new Admin" to the joining admin on a DS, the first time.

This means you shouldn't have to look up players steam IDs and add them to the server.cfg.
Unfortunately you do have to add this file to the server.cfg.