I've been writing some server code for handling users, and naturally, this involves keeping track of Playfab user IDs that correspond with players. Previously, I had been validating incoming player IDs by checking if they were exactly 16 characters. Today, I just noticed that some players were not being handled because because there apparently exist 15 character user IDs as well.
Are there any defined characteristics for the format of user IDs that Playfab will generate? Do I need to be expecting possible user Ids shorter or longer than 15-16 characters?