Allow for a central resource of hosts, instructors, and other resources that can be managed in one place and then assigned to experiences

We think creating a resource management pool to assign to experiences and time slots will be more powerful than our current hosts feature, which is just a text field and image. This means that a host, guide, instructor, room, boat...really anything can belong to any given experience and booking. Additionally, we plan to make those resources shareable (and finite, so they can run out) across more than one experience. For example, if Susan is an instructor and can be available to lead experiences A, B, or C, but she gets booked for experience A at 9am - 12pm, she won't be available for that same time for experiences B and C. Also, if it's another type of resource, such as a canoe or room, once that finite resource pool is assigned to an experience + time slot combo, it can't be assigned elsewhere until it's free again.