Send an email when you have been added as a collaborator on a collection

[seanmiller26]

Right now there is no indication of any kind that you have been added to another user's collection as a collaborator, contributor, or viewer. This would behave similarly to the email you get when added as a collaborator on a project.

I understand there may not be upcoming BE dev time to tackle this, but I'm writing it up for future reference.

[seanmiller26]

@lcjohnso