Current organization

The Organization entity will begin to scope data access for many code paths going forward. The majority of web requests will be isolated to an Organization. Some global web requests like instance administration will not be isolated to an Organization.

There is the need for a mechanism to add the current organization as a context around the "current" code paths. For instance, current_user bounds the authorization context for code paths. The current_user is defined at the start of a request, and then is accessible in a "global like" getter for the rest of the request. We need a similar kind of mechanism to define the current_organization.

Related to #427660 (closed) and #427730