Describes whether external services required by the application
should be set-up on the fly by an orchestrator library such as distage-framework-docker (Scene.Managed),
or whether the application should try to connect to external services
as if they already exist in the environment (Scene.Provided).
We call a set of external services required by the application a Scene,
etymology being that the running external services required by the application
are like a "scene" that the "staff" (the orchestrator) must prepare
for the "actor" (the application) to enter.