I believe if you set it to "access" mode in the port settings it automatically enables portfast.
Automatic edge port
MS switches will automatically place all ACCESS type interfaces into EDGE mode. This will cause for the interface to immediately transition the port into STP forwarding mode upon linkup. The port still participates in STP. So if the port is to be a part of the loop, the port eventually transitions into STP blocking mode.
Source:
https://documentation.meraki.com/MS/Deployment_Guides/Advanced_MS_Setup_Guide