refactor associated function Job::build into the following module-level functions:
build
build_on_state
add build_on_state so that the building logic does not require a StateProviderFactory. this should make it easier to isolate and test the building logic on a given state, moving in the direction of #13.
refactor associated function
Job::buildinto the following module-level functions:buildbuild_on_stateadd
build_on_stateso that the building logic does not require aStateProviderFactory. this should make it easier to isolate and test the building logic on a given state, moving in the direction of #13.