SmartThings Z-Wave hub.
To create user codes you will need to get some SmartApps (and a Device Handler if you want to use the advanced features of your Schlage Connect beyond just the lock/unlock like autolock, keypad control etc).
If you’re looking for a one stop shop for locks/user management and don’t mind signing up for access check our www.rboyapps.com for SmartApps and Device Handlers for integrating your lock with SmartThings (beyond just the lock/unlock which doesn’t require any special apps or device handlers). It has all the instructions required to install it and get you going. There are also some other options available around the community.
Make sure that your Schlage Connect has a Z-WAVE module installed, if you bought it without the Z-Wave module it won’t work with SmartThings.