Installing New panel
Since this has its own meter, it's its own service entrance, but put a ground bar in anyway

Since you're getting a separately metered drop from the utility (instead of running a feeder from another building on the property), it's a service entrance all its own, so a service bond between neutral and ground needs to be established here.  (In other words, the green screw or strap that makes the neutral-to-ground connection stays put.)

I would still get a ground bar (Square-D PK15GTAL) and install it in the panel, then land the grounds separately from the neutrals, though, as this makes converting the panel to run off a feeder at a later date rather easier.  (Having two services on the property can get...awkward if you want control of say outdoor lights from both buildings.)