[pkp/pkp-lib#7188] Adds number of user assignments on user assignment grid

[JhonathanLepidus]

Related to issue 7188.

[asmecher]

@JhonathanLepidus, I think this will unintentionally/unexpectedly affect the SubscriberSelectGridHandler class, which is a subclass of UserSelectGridHandler. It should only affect the participant assignment area.

[JhonathanLepidus]

Hi @asmecher , I checked this possible conflict and, luckily, it does not affect the SubscriberSelectGridHandler. This class inherits directly from GridHandler. However, it uses the class UserSelectGridCellProvider, but since it doesn't add the assignments column, it's not affected by the new code.