There may be a bigger issue with the design of the control, but I'm not sure I could solve it in this PR. It's a discussion worth having if one of us comes up with a better way to do it or we get a PR with the changes.

To address your first question, the constraints are owned by the contact picker, not the collection view. Based on the discussions we've had in the past, which I think make a lot of sense, the goal of the `MBContactPicker` class is to act as an all-in-one, opinionated control that manages the complexities of it's children and presents a simplified interface for developers. Passing the collection view is giving an insight into the plumbing that I think I want to avoid for the all-in-one solution. If the user wants to handle things differently, they could implement their own contact picker class that either subclasses or entirely eliminates `MBContactPicker`.