Spike: Stack Ownership Model/Guardianship

Ideas thus far:

new resource mapping type:
* entity mapping (Stack) as owner of resource (ERM)
* stack is owned by user (URM)
* this is a small brain remapping that brings in the idea of ERM, and have URM be a specific entity that maps those relationships

new role:
* owner, member, pkger/stack?

The issue contains only ERM/URM ownership ideas and proposed roles; no files, tests, or entry points are named. Start by clarifying the scope and affected project areas, then define what an agreed ownership and role model would include before implementation begins.

Written by the indexing model from the issue text.