Updating Character Inventory from Server

Hi, This is a pretty simple question but I'm not able to figure out the exact syntax of the calls. I have a server script which creates a character and adds inventory to it. I then want to update that characters inventory with custom data.

Is there an equivalent of currentPlayerId for the current character that is available on the cloud scripting by default? If not, what is the proper progression?

For the character I start with GrantCharacterToUser, which works. How do I then get that Character's Id to be able to run GetCharacterInventory and then UpdateUserInventoryItemCustomData? Sorry, I feel like there's a super simple/obvious way to do it but I think I'm not seeing the forest for the trees at this point.

Thanks