AutoLogin Mojang accounts
It allows players that have Mojang account to bypass the authentication process. If player founded with the Mojang API, they are treated as online player, meaning that client will get the encryption request etc. For more technical info, see #23.
You have to set online-mode to true in server.properties. Then set the premiumAutologin to true as well in EasyAuth's config file.
This will create a "mixed" online mode server - players that have purchased Minecraft will be able to skip the login process and will have online-styled UUIDs as well.
On the other hand, players that don't own the Mojang account, will have to register / login every time they join the server and will have offline-type UUIDs.
You can still force offline UUIDs for everyone by enabling forcedOfflineUuids in config file.
Note: this should be used only if you had your server running in offline mode, and you made the switch to use premiumAutoLogin AND your players already have e.g. villager discounts, which are based on uuid. Other things (advancements, playerdata) are migrated automatically, so think before enabling this. In case an online-mode player changes username, they'll loose all their stuff, unless you migrate it manually.
If you want to mark a player who has a Mojang account as "force-offline" (they will still have to login every time), you can put their name (lower case!) in the forcedOfflinePlayers list in config file.
They probably have same nickname as someone else's Mojang online account. You can allow them to join by adding them in forcedOfflinePlayers list with command auth addToForcedOffline <player>