Make Recent Items available providers an option group so extensions can extend it
Overview
I would like my custom entities to be available to the Recent Items block.
In CRM_Utils_Recent::getProviders()
there's a comment to make the hard-coded list into an Open Group. I agree. Let's make it so.
Current behaviour
Hard-coded list of some core entities.
Proposed behaviour
Create an option group and call it from this method.