To simplify logic in the system, a child lifetime scope is created for
each distinct configuration instance that is processed by Recyclarr. The
main driver for this is to avoid objects being reused between instances
and thus needing setup & teardown logic to deal with state.
Multiple path fragments are now supported in the built-in
`SubDirectory()` extension method, so there's no longer a need for the
custom `SubDir()` version.
It was previously located in Common, which I'm trying to gradually get
rid of. Supported services are ultimately determined by what is in the
guide, so that seems like the best place for it.